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  • PHP INTRODUCTION ↓

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    If you want to learn the basics of PHP, then you've come to the right place. The goal of this tutorial is to teach you the basics of PHP so that you can:

    • Customize PHP scripts that you download, so that they better fit your needs.
    • Begin to understand the working model of PHP, so you may begin to design your own PHP projects.
    • Give you a solid base in PHP, so as to make you more valuable in the eyes of future employers.

    PHP stands for PHP Hypertext Preprocessor.

    PHP - What is it?

    Taken directly from PHP's home, PHP.net, "PHP is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly."

    This is generally a good definition of PHP. However, it does contain a lot of terms you may not be used to. Another way to think of PHP is a powerful, behind the scenes scripting language that your visitors won't see!

    When someone visits your PHP webpage, your web server processes the PHP code. It then sees which parts it needs to show to visitors(content and pictures) and hides the other stuff(file operations, math calculations, etc.) then translates your PHP into HTML. After the translation into HTML, it sends the webpage to your visitor's web browser.

    PHP - What's it do?

    It is also helpful to think of PHP in terms of what it can do for you. PHP will allow you to:

    • Reduce the time to create large websites.
    • Create a customized user experience for visitors based on information that you have gathered from them.
    • Open up thousands of possibilities for online tools. Check out PHP - HotScripts for examples of the great things that are possible with PHP.
    • Allow creation of shopping carts for e-commerce websites.

    What You Should Know

    Before starting this tutorial it is important that you have a basic understanding and experience in the following:

    • HTML - Know the syntax and especially HTML Forms.
    • Basic programming knowledge - This isn't required, but if you have any traditional programming experience it will make learning PHP a great deal easier.

    Tutorial Overview

    This tutorial is aimed at the PHP novice and will teach you PHP from the ground up. If you want a drive-through PHP tutorial this probably is not the right tutorial for you.

    Remember, you should not try to plow through this tutorial in one sitting. Read a couple lessons, take a break, then do some more after the information has had some time to sink in.

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  • PHP INSTALLATION ↓

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    PHP - Necessary Setup

    To begin working with PHP you must first have access to either of the following:

    • A web hosting account that supports the use of PHP web pages and grants you access to MySQL databases. If you do not have a host, but are interested in signing up for one, we recommend that you first read our Web Host Guide to educate yourself about web hosting and avoid getting ripped off.
    • Have PHP and MySQL installed on your own computer. Read this lesson thorougly for more information on installing PHP.

    Although MySQL is not absolutely necessary to use PHP, MySQL and PHP are wonderful complements to one another and some topics covered in this tutorial will require that you have MySQL access.

    Installing PHP

    For those who are experienced enough to do this yourself, simply head over to PHP.net - Downloads and download the most recent version of PHP.

    However, if you are like most of us, you will most likely want to follow a guide to installing PHP onto your computer. These guides are kindly provided by PHP.net based on the operating system that you are using.

    Installing MySQL

    As we mentioned before, MySQL is not a requirement to use PHP, however they often go hand in hand.

    Visit MySQL's MySQL Installation Guide for help on installing MySQL.

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  • PHP SYNTAX ↓

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    PHP - Syntax

    Before we talk about PHP's syntax, let us first define what syntax is referring to.

    • Syntax - The rules that must be followed to write properly structured code.

    PHP's syntax and semantics are similar to most other programming languages (C, Java, Perl) with the addition that all PHP code is contained with a tag, of sorts. All PHP code must be contained within the following...

    PHP Code:

    <?php
    ?>
    
    or the shorthand PHP tag that requires shorthand support to be enabled
    on your server...
    
    <?
    ?>
    

    If you are writing PHP scripts and plan on distributing them, we suggest that you use the standard form (which includes the ?php) rather than the shorthand form. This will ensure that your scripts will work, even when running on other servers with different settings.

    How to Save Your PHP Pages

    If you have PHP inserted into your HTML and want the web browser to interpret it correctly, then you must save the file with a .php extension, instead of the standard .html extension. So be sure to check that you are saving your files correctly. Instead of index.html, it should be index.php if there is PHP code in the file.

    Example Simple HTML & PHP Page

    Below is an example of one of the easiest PHP and HTML page that you can create and still follow web standards.

    PHP and HTML Code:

    <html>
    <head>
    <title>My First PHP Page</title>
    </head>
    <body>
    <?php
    echo "Hello World!";
    ?>
    </body>
    </html>
    

    Display:

    Hello World!

    If you save this file (e.g. helloworld.php) and place it on PHP enabled server and load it up in your web browser, then you should see "Hello World!" displayed. If not, please check that you followed our example correctly.

    We used the PHP command echo to write "Hello World!" and we will be talking in greater depth about how echo is special later on in this tutorial.

    The Semicolon!

    As you may or may not have noticed in the above example, there was a semicolon after the line of PHP code. The semicolon signifies the end of a PHP statement and should never be forgotten. For example, if we repeated our "Hello World!" code several times, then we would need to place a semicolon at the end of each statement.

    PHP and HTML Code:

    <html>
    <head>
    <title>My First PHP Page</title>
    </head>
    <body>
    <?php
    echo "Hello World! ";
    echo "Hello World! ";
    echo "Hello World! ";
    echo "Hello World! ";
    echo "Hello World! ";
    ?>
    </body>
    </html>
    

    Display:

    Hello World! Hello World! Hello World! Hello World! Hello World!

    White Space

    As with HTML, whitespace is ignored between PHP statements. This means it is OK to have one line of PHP code, then 20 lines of blank space before the next line of PHP code. You can also press tab to indent your code and the PHP interpreter will ignore those spaces as well.

    PHP and HTML Code:

    <html>
    <head>
    <title>My First PHP Page</title>
    </head>
    <body>
    <?php
    echo "Hello World!";        
    
    
    
    	echo "Hello World!";
    
    
    ?>
    </body>
    </html>
    

    Display:

    Hello World!Hello World!

    This is perfectly legal PHP code.

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  • PHP-VARIABLES ↓

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    If you have never had any programming, Algebra, or scripting experience, then the concept of variables might be a new concept to you. A detailed explanation of variables is beyond the scope of this tutorial, but we've included a refresher crash course to guide you.

    A variable is a means of storing a value, such as text string "Hello World!" or the integer value 4. A variable can then be reused throughout your code, instead of having to type out the actual value over and over again. In PHP you define a variable with the following form:

    • $variable_name = Value;

    If you forget that dollar sign at the beginning, it will not work. This is a common mistake for new PHP programmers!

    Note: Also, variable names are case-sensitive, so use the exact same capitalization when using a variable. The variables $a_number and $A_number are different variables in PHP's eyes.

    A Quick Variable Example

    Say that we wanted to store the values that we talked about in the above paragraph. How would we go about doing this? We would first want to make a variable name and then set that equal to the value we want. See our example below for the correct way to do this.

    PHP Code:

    <?php
    $hello = "Hello World!";
    $a_number = 4;
    $anotherNumber = 8;
    ?>
    
    

    Note for programmers: PHP does not require variables to be declared before being initialized.

    PHP Variable Naming Conventions

    There are a few rules that you need to follow when choosing a name for your PHP variables.

    • PHP variables must start with a letter or underscore "_".
    • PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ .
    • Variables with more than one word should be separated with underscores. $my_variable
    • Variables with more than one word can also be distinguished with capitalization. $myVariable
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  • PHP ECO ↓

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    As you saw in the previous lesson, the PHP command echo is a means of outputting text to the web browser. Throughout your PHP career you will be using the echo command more than any other. So let's give it a solid perusal!

    Outputting a String

    To output a string, like we have done in previous lessons, use PHP echo. You can place either a string variable or you can use quotes, like we do below, to create a string that the echo function will output.

    PHP Code:

    <?php
    $myString = "Hello!";
    echo $myString;
    echo "<h5>I love using PHP!</h5>";
    ?>
    

    Display:

    Hello!
    I love using PHP!

    In the above example we output "Hello!" without a hitch. The text we are outputting is being sent to the user in the form of a web page, so it is important that we use proper HTML syntax!

    In our second echo statement we use echo to write a valid Header 5 HTML statement. To do this we simply put the <h5> at the beginning of the string and closed it at the end of the string. Just because you're using PHP to make web pages does not mean you can forget about HTML syntax!

    Careful When Echoing Quotes!

    It is pretty cool that you can output HTML with PHP. However, you must be careful when using HTML code or any other string that includes quotes! Echo uses quotes to define the beginning and end of the string, so you must use one of the following tactics if your string contains quotations:

    • Don't use quotes inside your string
    • Escape your quotes that are within the string with a backslash. To escape a quote just place a backslash directly before the quotation mark, i.e. \"
    • Use single quotes (apostrophes) for quotes inside your string.

    See our example below for the right and wrong use of echo:

    PHP Code:

    <?php
    // This won't work because of the quotes around specialH5!
    echo "<h5 class="specialH5">I love using PHP!</h5>";  
    
    // OK because we escaped the quotes!
    echo "<h5 class=\"specialH5\">I love using PHP!</h5>";  
    
    // OK because we used an apostrophe '
    echo "<h5 class='specialH5'>I love using PHP!</h5>";  
    ?>
    

    If you want to output a string that includes quotations, either use an apostrophe ( ' ) or escape the quotations by placing a backslash in front of it ( \" ). The backslash will tell PHP that you want the quotation to be used within the string and NOT to be used to end echo's string.

    Echoing Variables

    Echoing variables is very easy. The PHP developers put in some extra work to make the common task of echoing all variables nearly foolproof! No quotations are required, even if the variable does not hold a string. Below is the correct format for echoing a variable.

    PHP Code:

    <?php
    $my_string = "Hello Bob.  My name is: ";
    $my_number = 4;
    $my_letter = a;
    echo $my_string;
    echo $my_number;
    echo $my_letter;
    ?>
    

    Display:

    Hello Bob. My name is: 4a

    Echoing Variables and Text Strings

    You can also place variables inside of double-quoted strings (e.g. "string here and a $variable"). By putting a variable inside the quotes (" ") you are telling PHP that you want it to grab the string value of that variable and use it in the string. The example below shows an example of this cool feature.

    PHP Code:

    <?php
    $my_string = "Hello Bob.  My name is: ";
    echo "$my_string Bobettta <br />";
    echo "Hi, I'm Bob.  Who are you? $my_string <br />";
    echo "Hi, I'm Bob.  Who are you? $my_string Bobetta";
    ?>
    

    Display:

    Hello Bob. My name is: Bobetta
    Hi, I'm Bob. Who are you? Hello Bob. My name is:
    Hi, I'm Bob. Who are you? Hello Bob. My name is: Bobetta

    By placing variables inside a string you can save yourself some time and make your code easier to read, though it does take some getting used to. Remember to use double-quotes, single-quotes will not grab the value of the string. Single-quotes will just output the variable name to the string, like )$my_string), rather than (Hello Bob. My name is: ).

    PHP Echo - Not a Function

    Echo is not a function, rather it is a language construct. When you use functions in PHP, they have a very particular form, which we will be going over later. For now, just know that echo is a special tool that you'll come to know and love!

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  • PHP STRINGS ↓

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    PHP - String Creation

    Before you can use a string you have to create it! A string can be used directly in a function or it can be stored in a variable. Below we create the exact same string twice: first storing it into a variable and in the second case we send the string directly to echo.

    PHP Code:

    $my_string = "AIT - Unlock your potential!";
    echo "AIT - Unlock your potential!";
    echo $my_string;
    

    In the above example the first string will be stored into the variable $my_string, while the second string will be used in the echo and not be stored. Remember to save your strings into variables if you plan on using them more than once! Below is the output from our example code. They look identical just as we thought.

    Display:

    AIT - Unlock your potential! AIT - Unlock your potential!

    PHP - String Creation Single Quotes

    Thus far we have created strings using double-quotes, but it is just as correct to create a string using single-quotes, otherwise known as apostrophes.

    PHP Code:

    $my_string = 'AIT - Unlock your potential!';
    echo 'AIT - Unlock your potential!';
    echo $my_string;
    

    If you want to use a single-quote within the string you have to escape the single-quote with a backslash \ . Like this: \' !

    PHP Code:

    echo 'AIT - It\'s Neat!';
    

    PHP - String Creation Double-Quotes

    We have used double-quotes and will continue to use them as the primary method for forming strings. Double-quotes allow for many special escaped characters to be used that you cannot do with a single-quote string. Once again, a backslash is used to escape a character.

    PHP Code:

    $newline = "A newline is \n";
    $return = "A carriage return is \r";
    $tab = "A tab is \t";
    $dollar = "A dollar sign is \$";
    $doublequote = "A double-quote is \"";
    

    Note: If you try to escape a character that doesn't need to be, such as an apostrophe, then the backslash will show up when you output the string.

    These escaped characters are not very useful for outputting to a web page because HTML ignore extra white space. A tab, newline, and carriage return are all examples of extra (ignorable) white space. However, when writing to a file that may be read by human eyes these escaped characters are a valuable tool!

    PHP - String Creation Heredoc

    The two methods above are the traditional way to create strings in most programming languages. PHP introduces a more robust string creation tool called heredoc that lets the programmer create multi-line strings without using quotations. However, creating a string using heredoc is more difficult and can lead to problems if you do not properly code your string! Here's how to do it:

    PHP Code:

    $my_string = <<<TEST
    AITECHTONIC.com
    ALL IN ONE Tutorials
    Unlock your potential!
    TEST;
    
    echo $my_string;
    

    There are a few very important things to remember when using heredoc.

    • Use <<< and some identifier that you choose to begin the heredoc. In this example we chose TEST as our identifier.
    • Repeat the identifier followed by a semicolon to end the heredoc string creation. In this example that was TEST;
    • The closing sequence TEST; must occur on a line by itself and cannot be indented!

    Another thing to note is that when you output this multi-line string to a web page, it will not span multiple lines because we did not have any <br /> tags contained inside our string! Here is the output made from the code above.

    Display:

    AITECHTONIC.com ALL IN ONE Tutorials Unlock your potential!

    Once again, take great care in following the heredoc creation guidelines to avoid any headaches.

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  • PHP OPERATORS ↓

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    In all programming languages, operators are used to manipulate or perform operations on variables and values. You have already seen the string concatenation operator "." in the Echo Lesson and the assignment operator "=" in pretty much every PHP example so far.

    There are many operators used in PHP, so we have separated them into the following categories to make it easier to learn them all.

    • Assignment Operators
    • Arithmetic Operators
    • Comparison Operators
    • String Operators
    • Combination Arithmetic & Assignment Operators

    Assignment Operators

    Assignment operators are used to set a variable equal to a value or set a variable to another variable's value. Such an assignment of value is done with the "=", or equal character. Example:

    • $my_var = 4;
    • $another_var = $my_var;

    Now both $my_var and $another_var contain the value 4. Assignments can also be used in conjunction with arithmetic operators.

    Arithmetic Operators

    OperatorEnglishExample
    + Addition 2 + 4
    - Subtraction 6 - 2
    * Multiplication 5 * 3
    / Division 15 / 3
    % Modulus 43 % 10

    PHP Code:

    $addition = 2 + 4; 
    $subtraction = 6 - 2; 
    $multiplication = 5 * 3; 
    $division = 15 / 3; 
    $modulus = 5 % 2; 
    echo "Perform addition: 2 + 4 = ".$addition."<br />"; 
    echo "Perform subtraction: 6 - 2 = ".$subtraction."<br />"; 
    echo "Perform multiplication:  5 * 3 = ".$multiplication."<br />"; 
    echo "Perform division: 15 / 3 = ".$division."<br />"; 
    echo "Perform modulus: 5 % 2 = " . $modulus 
    	. ". Modulus is the remainder after the division operation has been performed.  
    	In this case it was 5 / 2, which has a remainder of 1.";
    

    Display:

    Perform addition: 2 + 4 = 6
    Perform subtraction: 6 - 2 = 4
    Perform multiplication: 5 * 3 = 15
    Perform division: 15 / 3 = 5
    Perform modulus: 5 % 2 = 1. Modulus is the remainder after the division operation has been performed. In this case it was 5 / 2, which has a remainder of 1.

    Comparison Operators

    Comparisons are used to check the relationship between variables and/or values. If you would like to see a simple example of a comparison operator in action, check out our If Statement Lesson. Comparison operators are used inside conditional statements and evaluate to either true or false. Here are the most important comparison operators of PHP.
    Assume: $x = 4 and $y = 5;

    OperatorEnglish Example Result
    == Equal To $x == $y false
    != Not Equal To $x != $y true
    < Less Than $x < $y true
    > Greater Than $x > $y false
    <= Less Than or Equal To $x <= $y true
    >= Greater Than or Equal To $x >= $y false

    String Operators

    As we have already seen in the Echo Lesson, the period "." is used to add two strings together, or more technically, the period is the concatenation operator for strings.

    PHP Code:

    $a_string = "Hello";
    $another_string = " Billy";
    $new_string = $a_string . $another_string;
    echo $new_string . "!";
    

    Display:

    Hello Billy!

    Combination Arithmetic & Assignment Operators

    In programming it is a very common task to have to increment a variable by some fixed amount. The most common example of this is a counter. Say you want to increment a counter by 1, you would have:

    • $counter = $counter + 1;

    However, there is a shorthand for doing this.

    • $counter += 1;

    This combination assignment/arithmetic operator would accomplish the same task. The downside to this combination operator is that it reduces code readability to those programmers who are not used to such an operator. Here are some examples of other common shorthand operators. In general, "+=" and "-=" are the most widely used combination operators.

    OperatorEnglish Example Equivalent Operation
    +=Plus Equals $x += 2; $x = $x + 2;
    -=Minus Equals $x -= 4; $x = $x - 4;
    *=Multiply Equals $x *= 3; $x = $x * 3;
    /=Divide Equals $x /= 2; $x = $x / 2;
    %=Modulo Equals $x %= 5; $x = $x % 5;
    .=Concatenate Equals $my_str.="hello"; $my_str = $my_str . "hello";

    Pre/Post-Increment & Pre/Post-Decrement

    This may seem a bit absurd, but there is even a shorter shorthand for the common task of adding 1 or subtracting 1 from a variable. To add one to a variable or "increment" use the "++" operator:

    • $x++; Which is equivalent to $x += 1; or $x = $x + 1;

    To subtract 1 from a variable, or "decrement" use the "--" operator:

    • $x--; Which is equivalent to $x -= 1; or $x = $x - 1;

    In addition to this "shorterhand" technique, you can specify whether you want to increment before the line of code is being executed or after the line has executed. Our PHP code below will display the difference.

    PHP Code:

    $x = 4;
    echo "The value of x with post-plusplus = " . $x++;
    echo "<br /> The value of x after the post-plusplus is " . $x;
    $x = 4;
    echo "<br />The value of x with with pre-plusplus = " . ++$x;
    echo "<br /> The value of x after the pre-plusplus is " . $x;
    

    Display:

    The value of x with post-plusplus = 4
    The value of x after the post-plusplus is = 5
    The value of x with with pre-plusplus = 5
    The value of x after the pre-plusplus is = 5

    As you can see the value of $x++ is not reflected in the echoed text because the variable is not incremented until after the line of code is executed. However, with the pre-increment "++$x" the variable does reflect the addition immediately.

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  • PHP COMMENTS ↓

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    Using Comments in PHP

    Comments in PHP are similar to comments that are used in HTML. The PHP comment syntax always begins with a special character sequence and all text that appears between the start of the comment and the end will be ignored.

    In HTML a comment's main purpose is to serve as a note to you, the web developer or to others who may view your website's source code. However, PHP's comments are different in that they will not be displayed to your visitors. The only way to view PHP comments is to open the PHP file for editing. This makes PHP comments only useful to PHP programmers.

    In case you forgot what an HTML comment looked like, see our example below.

    HTML Code:

    <!-- This is an HTML Comment -->
    

    PHP Comment Syntax: Single Line Comment

    While there is only one type of comment in HTML, PHP has two types. The first type we will discuss is the single line comment. The single line comment tells the interpreter to ignore everything that occurs on that line to the right of the comment. To do a single line comment type "//" or "#" and all text to the right will be ignored by PHP interpreter.

    PHP Code:

    <?php
    echo "Hello World!"; // This will print out Hello World!
    echo "<br />Psst...You can't see my PHP comments!"; // echo "nothing";
    // echo "My name is Humperdinkle!";
    # echo "I don't do anything either";
    ?>
    

    Display:

    Hello World!
    Psst...You can't see my PHP comments!

    Notice that a couple of our echo statements were not evaluated because we commented them out with the single line comment. This type of line commenting is often used for quick notes about complex and confusing code or to temporarily remove a line of PHP code.

    PHP Comment Syntax: Multiple Line Comment

    Similiar to the HTML comment, the multi-line PHP comment can be used to comment out large blocks of code or writing multiple line comments. The multiple line PHP comment begins with " /* " and ends with " */ ".

    PHP Code:

    <?php
    /* This Echo statement will print out my message to the
    the place in which I reside on.  In other words, the World. */
    echo "Hello World!"; 
    /* echo "My name is Humperdinkle!";
    echo "No way! My name is Uber PHP Programmer!";
    */
    ?>
    

    Display:

    Hello World!

    Good Commenting Practices

    One of the best commenting practices that I can recommend to new PHP programmers is....USE THEM!! So many people write complex PHP code and are either too lazy to write good comments or believe the commenting is not needed. However, do you really believe that you will remember exactly what you were thinking when looking at this code a year or more down the road?

    Let the comments permeate your code and you will be a happier PHPer in the future. Use single line comments for quick notes about a tricky part in your code and use multiple line comments when you need to describe something in greater depth than a simple note.

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  • PHP INCLUDE ↓

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    Without understanding much about the details of PHP, you can save yourself a great deal of time with the use of the PHP include command. include takes a file name and simply inserts that file's contents into the script that issued the include command.

    Why is this a cool thing? Well, first of all, this means that you can type up a common header or menu file that you want all your web pages to include. When you add a new page to your site, instead of having to update the links on several web pages, you can simply change the Menu file.

    An Include Example

    Say we wanted to create a common menu file that all our pages will use. A common practice for naming files that are to be included is to use the ".php" extension. Since we want to create a common menu let's save it as "menu.php".

    menu.php Code:

    <html>
    <body>
    <a href="http://www.example.com/index.php">Home</a> - 
    <a href="http://www.example.com/about.php">About Us</a> - 
    <a href="http://www.example.com/links.php">Links</a> - 
    <a href="http://www.example.com/contact.php">Contact Us</a> <br />
    

    Save the above file as "menu.php". Now create a new file, "index.php" in the same directory as "menu.php". Here we will take advantage of the include command to add our common menu.

    index.php Code:

    <?php include("menu.php"); ?>
    <p>This is my home page that uses a common menu to save me time when I add
    new pages to my website!</p>
    </body>
    </html>
    

    Display:

    Home - About Us - Links - Contact Us

    This is my home page that uses a common menu to save me time when I add new pages to my website!

    And we would do the same thing for "about.php", "links.php", and "contact.php". Just think how terrible it would be if you had 15 or more pages with a common menu and you decided to add another web page to that site. You would have to go in and manually edit every single file to add this new page, but with include files you simply have to change "menu.php" and all your problems are solved. Avoid such troublesome occasions with a simple include file.

    What do Visitors See?

    If we were to use the include command to insert a menu on each of our web pages, what would the visitor see if they viewed the source of "index.php"? Well, because the include command is pretty much the same as copying and pasting, the visitors would see:

    View Source of index.php to a Visitor:

    <html>
    <body>
    <a href="index.php">Home</a> - 
    <a href="about.php">About Us</a> - 
    <a href="links.php">Links</a> - 
    <a href="contact.php">Contact Us</a> <br />
    <p>This is my home page that uses a common menu to save me time when I add
    new pages to my website!</p>
    </body>
    </html>
    

    The visitor would actually see all the HTML code as one long line of HTML code, because we have not inserted any new line characters. We did some formatting above to make it easier to read. We will be discussing new line characters later.

    Include Recap

    The include command simply takes all the text that exists in the specified file and copies it into the file that uses the include command. Include is quite useful when you want to include the same PHP, HTML, or text segment on multiple pages of a website. The include command is used widely by PHP web developers. Like PHP Echo, include is not a function, but a language construct.

    The next lesson will talk about a slight variation of the include command: require. It is often best to use the require command instead of the include command in your PHP Code. Read the next lesson to find out why!

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  • PHP REQUIRE ↓

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    Just like the previous lesson, the require command is used to include a file into your PHP code. However there is one huge difference between the two commands, though it might not seem that big of a deal.

    Require vs Include

    When you include a file with the include command and PHP cannot find it you will see an error message like the following:

    PHP Code:

    <?php
    include("noFileExistsHere.php");
    echo "Hello World!";
    ?>
    

    Display:

    Warning: main(noFileExistsHere.php): failed to open stream: No such file or directory in /home/websiteName/FolderName/AITScript.php on line 2 Warning: main(): Failed opening 'noFileExistsHere.php' for inclusion (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/websiteName/FolderName/AITScript.php on line 2

    Hello World!

    Notice that our echo statement is still executed, this is because a Warning does not prevent our PHP script from running. On the other hand, if we did the same example but used the require statement we would get something like the following example.

    PHP Code:

    <?php
    require("noFileExistsHere.php");
    echo "Hello World!";
    ?>
    

    Display:

    Warning: main(noFileExistsHere.php): failed to open stream: No such file or directory in /home/websiteName/FolderName/AITScript.php on line 2
    Fatal error: main(): Failed opening required 'noFileExistsHere.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/websiteName/FolderName/AITScript.php on line 2

    The echo statement was not executed because our script execution died after the require command returned a fatal error! We recommend that you use require instead of include because your scripts should not be executing if necessary files are missing or misnamed.

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  • PHP CONDITIONS ↓

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    The If Statement

    The PHP if statement is very similar to other programming languages use of the if statement, but for those who are not familiar with it, picture the following:

    Think about the decisions you make before you go to sleep. If you have something to do the next day, say go to work, school, or an appointment, then you will set your alarm clock to wake you up. Otherwise, you will sleep in as long as you like!

    This simple kind of if/then statement is very common in every day life and also appears in programming quite often. Whenever you want to make a decision given that something is true (you have something to do tomorrow) and be sure that you take the appropriate action, you are using an if/then relationship.

    The PHP If Statement

    The if statement is necessary for most programming, thus it is important in PHP. Imagine that on January 1st you want to print out "Happy New Year!" at the top of your personal web page. With the use of PHP if statements you could have this process automated, months in advance, occuring every year on January 1st.

    This idea of planning for future events is something you would never have had the opportunity of doing if you had just stuck with HTML.

    If Statement Example

    The "Happy New Year" example would be a little difficult for you to do right now, so let us instead start off with the basics of the if statement. The PHP if statement tests to see if a value is true, and if it is a segment of code will be executed. See the example below for the form of a PHP if statement.

    PHP Code:

    $my_name = "someguy";
    
    if ( $my_name == "someguy" ) {
    	echo "Your name is someguy!<br />";
    }
    echo "Welcome to my homepage!";
    

    Display:

    Your name is someguy!
    Welcome to my homepage!

    Did you get that we were comparing the variable $my_name with "someguy" to see if they were equal? In PHP you use the double equal sign (==) to compare values. Additionally, notice that because the if statement turned out to be true, the code segment was executed, printing out "Your name is someguy!". Let's go a bit more in-depth into this example to iron out the details.

    • We first set the variable $my_name equal to "someguy".
    • We next used a PHP if statement to check if the value contained in the variable $my_name was equal to "someguy"
    • The comparison between $my_name and "someguy" was done with a double equal sign "==", not a single equals"="! A single equals is for assigning a value to a variable, while a double equals is for checking if things are equal.
    • Translated into english the PHP statement ( $my_name == "someguy" ) is ( $my_name is equal to "someguy" ).
    • $my_name is indeed equal to "someguy" so the echo statement is executed.

    A False If Statement

    Let us now see what happens when a PHP if statement is not true, in other words, false. Say that we changed the above example to:

    PHP Code:

    $my_name = "anotherguy";
    
    if ( $my_name == "someguy" ) {
    	echo "Your name is someguy!<br />";
    }
    echo "Welcome to my homepage!";
    

    Display:

    Welcome to my homepage!

    Here the variable contained the value "anotherguy", which is not equal to "someguy". The if statement evaluated to false, so the code segment of the if statement was not executed. When used properly, the if statement is a powerful tool to have in your programming arsenal!

    If/Else Conditional Statment

    Has someone ever told you, "if you work hard, then you will succeed"? And what happens if you do not work hard? Well, you fail! This is an example of an if/else conditional statement.

    • If you work hard then you will succeed.
    • Else, if you do not work hard, then you will fail.

    How does this translate into something useful for PHP developers? Well consider this:

    Someone comes to your website and you want to ask this visitor her name if it is her first time coming to your site. With an if statement this is easy. Simply have a conditional statement to check, "are you visiting for the first time". If the condition is true, then take them to the "Insert Your Name" page, else let her view the website as normal because you have already asked her for her name in the past.

    If/Else an Example

    Using these conditional statements can add a new layers of "cool" to your website. Here's the basic form of an if/else statement in PHP.

    PHP Code:

    $number_three = 3;
    
    if ( $number_three == 3 ) {
    	echo "The if statement evaluated to true";
    } else {
    	echo "The if statement evaluated to false";
    }
    

    Display:

    The if statement evaluated to true

    This is a lot to digest in one sitting, so let us step through the code, line by line.

    • We first made a PHP variable called $number_three and set it equal to 3.
    • In this example we compared a variable to an integer value. To do such a comparison we use "==", which in English means "Is Equal To".
    • $number_three is indeed Equal To 3 and so this statement will evaluate to true.
    • All code that is contained between the opening curly brace "{" that follows the if statement and the closing curly brace "}" will be executed when the if statement is true.
    • The code contained within the else segment will not used.

    Execute Else Code with False

    On the other hand, if the if statement was false, then the code contained in the else segment would have been executed. Note that the code within the if and else cannot both be executed, as the if statement cannot evaluate to both true and false at one time! Here is what would happen if we changed to $number_three to anything besides the number 3.

    PHP Code:

    $number_three = 421;
    
    if ( $number_three == 3 ) {
    	echo "The if statement evaluated to true";
    } else {
    	echo "The if statement evaluated to false";
    }
    

    Display:

    The if statement evaluated to false

    The variable was set to 421, which is not equal to 3 and the if statement was false. As you can see, the code segment contained within the else was used in this case.

    PHP - Elseif

    An if/else statement is great if you only need to check for one condition. However, what would you do if you wanted to check if your $employee variable was the company owner Bob, the Vice President Ms. Tanner, or a regular employee? To check for these different conditions you would need the elseif statement.

    PHP - Elseif What is it?

    An if statement is made up of the keyword "if" and a conditional statement (i.e. $name == "Ted"). Just like an if statement, an elseif statement also contains a conditional statement, but it must be preceded by an if statement. You cannot have an elseif statement without first having an if statement.

    When PHP evaluates your If...elseif...else statement it will first see if the If statement is true. If that tests comes out false it will then check the first elseif statement. If that is false it will either check the next elseif statement, or if there are no more elseif statements, it will evaluate the else segment, if one exists (I don't think I've ever used the word "if" so much in my entire life!). Let's take a look at a real world example.

    PHP - Using Elseif with If...Else

    Let's start out with the base case. Imagine we have a simpler version of the problem described above. We simply want to find out if the employee is the Vice President Ms. Tanner. We only need an if else statement for this part of the example.

    PHP Code:

    $employee = "Bob";
    if($employee == "Ms. Tanner"){
    	echo "Hello Ma'am";
    } else {
    	echo "Morning";
    }
    

    Now, if we wanted to also check to see if the big boss Bob was the employee we need to insert an elseif clause.

    PHP Code:

    $employee = "Bob";
    if($employee == "Ms. Tanner"){
    	echo "Hello Ma'am";
    } elseif($employee == "Bob"){
    	echo "Good Morning Sir!";
    }else {
    	echo "Morning";
    }
    

    Display:

    Good Morning Sir!

    PHP first checked to see if $employee was equal to "Ms. Tanner", which evaluated to false. Next, PHP checked the first elseif statement. $employee did in fact equal "Bob" so the phrase "Good Morning Sir!" was printed out. If we wanted to check for more employee names we could insert more elseif statements!

    Remember that an elseif statement cannot be used unless it is preceded by an if statement!

    PHP Switch Statement

    In the previous lessons we covered the various elements that make up an If Statement in PHP. However, there are times when an if statement is not the most efficient way to check for certain conditions.

    For example we might have a variable that stores travel destinations and you want to pack according to this destination variable. In this example you might have 20 different locations that you would have to check with a nasty long block of If/ElseIf/ElseIf/ElseIf/... statements. This doesn't sound like much fun to code, let's see if we can do something different.

    PHP Switch Statement: Speedy Checking

    With the use of the switch statement you can check for all these conditions at once, and the great thing is that it is actually more efficient programming to do this. A true win-win situation!

    The way the Switch statement works is it takes a single variable as input and then checks it against all the different cases you set up for that switch statement. Instead of having to check that variable one at a time, as it goes through a bunch of If Statements, the Switch statement only has to check one time.

    PHP Switch Statement Example

    In our example the single variable will be $destination and the cases will be: Las Vegas, Amsterdam, Egypt, Tokyo, and the Caribbean Islands.

    PHP Code:

    $destination = "Tokyo";
    echo "Traveling to $destination<br />";
    switch ($destination){
    	case "Las Vegas":
    		echo "Bring an extra $500";
    		break;
    	case "Amsterdam":
    		echo "Bring an open mind";
    		break;	
    	case "Egypt":
    		echo "Bring 15 bottles of SPF 50 Sunscreen";
    		break;	
    	case "Tokyo":
    		echo "Bring lots of money";
    		break;
    	case "Caribbean Islands":
    		echo "Bring a swimsuit";
    		break;	
    }
    

    Display:

    Traveling to Tokyo
    Bring lots of money

    The value of $destination was Tokyo, so when PHP performed the switch operating on $destination in immediately did a search for a case with the value of "Tokyo". It found it and proceeded to execute the code that existed within that segment.

    You might have noticed how each case contains a break; at the end of its code area. This break prevents the other cases from being executed. If the above example did not have any break statements then all the cases that follow Tokyo would have been executed as well. Use this knowledge to enhance the power of your switch statements!

    The form of the switch statement is rather unique, so spend some time reviewing it before moving on. Note: Beginning programmers should always include the break; to avoid any unnecessary confusion.

    PHP Switch Statement: Default Case

    You may have noticed the lack of a place for code when the variable doesn't match our condition. The if statement has the else clause and the switch statement has the default case.

    It's usually a good idea to always include the default case in all your switch statements. Below is a variation of our example that will result in none of the cases being used causing our switch statement to fall back and use the default case. Note: the word case does not appear before the word default, as default is a special keyword!

    PHP Code:

    $destination = "New York";
    echo "Traveling to $destination<br />";
    switch ($destination){
    	case "Las Vegas":
    		echo "Bring an extra $500";
    		break;
    	case "Amsterdam":
    		echo "Bring an open mind";
    		break;
    	case "Egypt":
    		echo "Bring 15 bottles of SPF 50 Sunscreen";
    		break;	
    	case "Tokyo":
    		echo "Bring lots of money";
    		break;	
    	case "Caribbean Islands":
    		echo "Bring a swimsuit";
    		break; 	
    	default:
    		echo "Bring lots of underwear!";
    		break;
    }
    

    Display:

    Traveling to New York
    Bring lots of underwear!
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  • PHP LOOPS ↓

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    PHP - While Loop

    Repetitive tasks are always a burden to us. Deleting spam email, sealing 50 envelopes, and going to work are all examples of tasks that are repeated. The nice thing about programming is that you can avoid such repetitive tasks with a little bit of extra thinking. Most often these repetitive tasks are conquered in the loop.

    The idea of a loop is to do something over and over again until the task has been completed. Before we show a real example of when you might need one, let's go over the structure of the PHP while loop.

    Simple While Loop Example

    The function of the while loop is to do a task over and over as long as the specified conditional statement is true. This logical check is the same as the one that appears in a PHP if statement to determine if it is true or false. Here is the basic structure of a PHP while loop:

    Pseudo PHP Code:

    while ( conditional statement is true){
    	//do this code;
    }
    

    This isn't valid PHP code, but it displays how the while loop is structured. Here is the break down of how a while loop functions when your script is executing:

    1. The conditional statement is checked. If it is true, then (2) occurs. If it is false, then (4) occurs.
    2. The code within the while loop is executed.
    3. The process starts again at (1). Effectively "looping" back.
    4. If the conditional statement is false, then the code within is not executed and there is no more looping. The code following the while loop is then executed like normal.

    A Real While Loop Example

    Imagine that you are running an art supply store. You would like to print out the price chart for number of brushes and total cost. You sell brushes at a flat rate, but would like to display how much different quantities would cost. This will save your customers from having to do the mental math themselves.

    You know that a while loop would be perfect for this repetitive and boring task. Here is how to go about doing it.

    Pseudo PHP Code:

    $brush_price = 5; 
    $counter = 10;
    
    echo "<table border=\"1\" align=\"center\">";
    echo "<tr><th>Quantity</th>";
    echo "<th>Price</th></tr>";
    while ( $counter <= 100 ) {
    	echo "<tr><td>";
    	echo $counter;
    	echo "</td><td>";
    	echo $brush_price * $counter;
    	echo "</td></tr>";
    	$counter = $counter + 10;
    }
    echo "</table>";
    

    Display:

    QuantityPrice
    1050
    20100
    30150
    40200
    50250
    60300
    70350
    80400
    90450
    100500

    Pretty neat, huh? The loop created a new table row and its respective entries for each quantity, until our counter variable grew past the size of 100. When it grew past 100 our conditional statement failed and the loop stopped being used. Let's review what is going on.

    1. We first made a $brush_price and $counter variable and set them equal to our desired values.
    2. The table was set up with the beginning table tag and the table headers.
    3. The while loop conditional statement was checked, and $counter (10) was indeed smaller or equal to 100.
    4. The code inside the while loop was executed, creating a new table row for the price of 10 brushes.
    5. We then added 10 to $counter to bring the value to 20.
    6. The loop started over again at step 3, until $counter grew larger than 100.
    7. After the loop had completed, we ended the table.

    You may have noticed that we placed slashes infront the quotations in the first echo statement. You have to place slashes before quotations if you do not want the quotation to act as the end of the echo statement. This is called escaping a character and it is discussed in our PHP Strings lesson.

    With proper use of loops you can complete large tasks with great ease.

    PHP - For Loop

    The for loop is simply a while loop with a bit more code added to it. The common tasks that are covered by a for loop are:

    1. Set a counter variable to some initial value.
    2. Check to see if the conditional statement is true.
    3. Execute the code within the loop.
    4. Increment a counter at the end of each iteration through the loop.

    The for loop allows you to define these steps in one easy line of code. It may seem to have a strange form, so pay close attention to the syntax used!

    For Loop Example

    Let us take the example from the while loop lesson and see how it could be done in a for loop. The basic structure of the for loop is as follows:

    Pseudo PHP Code:

    for ( initialize a counter; conditional statement; increment a counter){
    	do this code;
    }
    

    Notice how all the steps of the loop are taken care of in the for loop statement. Each step is separated by a semicolon: initiliaze counter, conditional statement, and the counter increment. A semicolon is needed because these are separate expressions. However, notice that a semicolon is not needed after the "increment counter" expression.

    Here is the example of the brush prices done with a for loop .

    PHP Code:

    $brush_price = 5; 
    
    echo "<table border=\"1\" align=\"center\">";
    echo "<tr><th>Quantity</th>";
    echo "<th>Price</th></tr>";
    for ( $counter = 10; $counter <= 100; $counter += 10) {
    	echo "<tr><td>";
    	echo $counter;
    	echo "</td><td>";
    	echo $brush_price * $counter;
    	echo "</td></tr>";
    }
    echo "</table>";
    

    Display:

    QuantityPrice
    1050
    20100
    30150
    40200
    50250
    60300
    70350
    80400
    90450
    100500

    It is important to note that both the for loop and while loop implementation of the price chart table are both OK at getting the job done. However, the for loop is somewhat more compact and would be preferable in this situation. In later lessons we will see where the while loop should be used instead of the for loop.

    PHP For Each Loop

    Imagine that you have an associative array that you want to iterate through. PHP provides an easy way to use every element of an array with the Foreach statement.

    In plain english this statement will do the following:

    • For each item in the specified array execute this code.

    While a For Loop and While Loop will continue until some condition fails, the For Each loop will continue until it has gone through every item in the array.

    PHP For Each: Example

    We have an associative array that stores the names of people in our company as the keys with the values being their age. We want to know how old everyone is at work so we use a Foreach loop to print out everyone's name and age.

    PHP Code:

    $employeeAges;
    $employeeAges["Lisa"] = "28";
    $employeeAges["Jack"] = "16";
    $employeeAges["Ryan"] = "35";
    $employeeAges["Rachel"] = "46";
    $employeeAges["Grace"] = "34";
    
    foreach( $employeeAges as $key => $value){
    	echo "Name: $key, Age: $value <br />";
    }
    

    Display:

    Name: Lisa, Age: 28
    Name: Jack, Age: 16
    Name: Ryan, Age: 35
    Name: Rachel, Age: 46
    Name: Grace, Age: 34

    The syntax of the foreach statement is a little strange, so let's talk about it some.

    Foreach Syntax: $something as $key => $value

    This crazy statement roughly translates into: For each element of the $employeeAges associative array I want to refer to the key as $key and the value as $value.

    The operator "=>" represents the relationship between a key and value. You can imagine that the key points => to the value. In our example we named the key $key and the value $value. However, it might be easier to think of it as $name and $age. Below our example does this and notice how the output is identical because we only changed the variable names that refer to the keys and values.

    PHP Code:

    $employeeAges;
    $employeeAges["Lisa"] = "28";
    $employeeAges["Jack"] = "16";
    $employeeAges["Ryan"] = "35";
    $employeeAges["Rachel"] = "46";
    $employeeAges["Grace"] = "34";
    
    foreach( $employeeAges as $name => $age){
    	echo "Name: $name, Age: $age <br />";
    }
    

    Display:

    Name: Lisa, Age: 28
    Name: Jack, Age: 16
    Name: Ryan, Age: 35
    Name: Rachel, Age: 46
    Name: Grace, Age: 34

    PHP - Do While Loop

    A "do while" loop is a slightly modified version of the while loop. If you recal from one of the previous lessons on While Loops the conditional statement is checked comes back true then the code within the while loop is executed. If the conditional statement is false then the code within the loop is not executed.

    On the other hand, a do-while loop always executes its block of code at least once. This is because the conditional statement is not checked until after the contained code has been executed.

    PHP - While Loop and Do While Loop Contrast

    A simple example that illustrates the difference between these two loop types is a conditional statement that is always false. First the while loop:

    PHP Code:

    $cookies = 0;
    while($cookies > 1){
    	echo "Mmmmm...I love cookies! *munch munch munch*";
    } 
    

    Display:


    As you can see, this while loop's conditional statement failed (0 is not greater than 1), which means the code within the while loop was not executed. Now, can you guess what will happen with a do-while loop?

    PHP Code:

    $cookies = 0;
    do {
    	echo "Mmmmm...I love cookies! *munch munch munch*";
    } while ($cookies > 1);
    

    Display:

    Mmmmm...I love cookies! *munch munch munch*

    The code segment "Mmmm...I love cookies!" was executed even though the conditional statement was false. This is because a do-while loop first do's and secondly checks the while condition!

    Chances are you will not need to use a do while loop in most of your PHP programming, but it is good to know it's there!

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  • PHP ARRAY ↓

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    An array is a data structure that stores one or more values in a single value. For experienced programmers it is important to note that PHP's arrays are actually maps (each key is mapped to a value).

    PHP - A Numerically Indexed Array

    If this is your first time seeing an array, then you may not quite understand the concept of an array. Imagine that you own a business and you want to store the names of all your employees in a PHP variable. How would you go about this?

    It wouldn't make much sense to have to store each name in its own variable. Instead, it would be nice to store all the employee names inside of a single variable. This can be done, and we show you how below.

    PHP Code:

    $employee_array[0] = "Bob";
    $employee_array[1] = "Sally";
    $employee_array[2] = "Charlie";
    $employee_array[3] = "Clare";
    

    In the above example we made use of the key / value structure of an array. The keys were the numbers we specified in the array and the values were the names of the employees. Each key of an array represents a value that we can manipulate and reference. The general form for setting the key of an array equal to a value is:

    • $array[key] = value;

    If we wanted to reference the values that we stored into our array, the following PHP code would get the job done.

    Note: As you may have noticed from the above code example, an array's keys start from 0 and not 1. This is a very common problem for many new programmers who are used to counting from 1 and lead to "off by 1" errors. This is just something that will take experience before you are fully comfortable with it.

    PHP Code:

    echo "Two of my employees are "
    . $employee_array[0] . " & " . $employee_array[1]; 
    echo "<br />Two more employees of mine are " 
    . $employee_array[2] . " & " . $employee_array[3];
    

    Display:

    Two of my employees are Bob & Sally
    Two more employees of mine are Charlie & Clare

    PHP arrays are quite useful when used in conjunction with loops, which we will talk about in a later lesson. Above we showed an example of an array that made use of integers for the keys (a numerically indexed array). However, you can also specify a string as the key, which is referred to as an associative array.

    PHP - Associative Arrays

    In an associative array a key is associated with a value. If you wanted to store the salaries of your employees in an array, a numerically indexed array would not be the best choice. Instead, we could use the employees names as the keys in our associative array, and the value would be their respective salary.

    PHP Code:

    $salaries["Bob"] = 2000;
    $salaries["Sally"] = 4000;
    $salaries["Charlie"] = 600;
    $salaries["Clare"] = 0;
    
    echo "Bob is being paid - $" . $salaries["Bob"] . "<br />";
    echo "Sally is being paid - $" . $salaries["Sally"] . "<br />";
    echo "Charlie is being paid - $" . $salaries["Charlie"] . "<br />";
    echo "Clare is being paid - $" . $salaries["Clare"];
    

    Display:

    Bob is being paid - $2000
    Sally is being paid - $4000
    Charlie is being paid - $600
    Clare is being paid - $0

    Once again, the usefulness of arrays will become more apparent once you have knowledge of for and while loops.

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  • PHP FORM ↓

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    Using PHP With HTML Forms

    It is time to apply the knowledge you have obtained thus far and put it to real use. A very common application of PHP is to have an HTML form gather information from a website's visitor and then use PHP to do process that information. In this lesson we will simulate a small business's website that is implementing a very simple order form.

    Imagine we are an art supply store that sells brushes, paint, and erasers. To gather order information from our prospective customers we will have to make a page with an HTML form to gather the customer's order.

    Note: This is an oversimplified example to educate you how to use PHP to process HTML form information. This example is not intended nor advised to be used on a real business website.

    Creating the HTML Form

    If you need a refresher on how to properly make an HTML form, check out the HTML Form Lesson before continuing on.

    We first create an HTML form that will let our customer choose what they would like to purchase. This file should be saved as "order.html"

    .

    order.html Code:

    <html><body>
    <h4>AIT Art Supply Order Form</h4>
    <form> 
    <select> 
    <option>Paint</option>
    <option>Brushes</option>
    <option>Erasers</option>
    </select>
    Quantity: <input type="text" /> 
    <input type="submit" />
    </form>
    </body></html>
    

    Display:

    AIT Art Supply Order Form

    Quantity:

    Remember to review HTML Forms if you do not understand any of the above HTML code. Next we must alter our HTML form to specify the PHP page we wish to send this information to. Also, we set the method to "post".

    order.html Code:

    <html><body>
    <h4>AIT Art Supply Order Form</h4>
    <form action="process.php" method="post"> 
    <select name="item"> 
    <option>Paint</option>
    <option>Brushes</option>
    <option>Erasers</option>
    </select>
    Quantity: <input name="quantity" type="text" /> 
    <input type="submit" />
    </form>
    </body></html>
    

    Now that our "order.html" is complete, let us continue on and create the "process.php" file which will process the HTML form information.

    PHP Form Processor

    We want to get the "item" and "quantity" inputs that we have specified in our HTML form. Using an associative array (this term is explained in the array lesson), we can get this information from the $_POST associative array.

    The proper way to get this information would be to create two new variables, $item and $quantity and set them equal to the values that have been "posted". The name of this file is "process.php".

    process.php Code:

    <html><body>
    <?php
    $quantity = $_POST['quantity'];
    $item = $_POST['item'];
    
    echo "You ordered ". $quantity . " " . $item . ".<br />";
    echo "Thank you for ordering from AIT Art Supplies!";
    
    ?>
    </body></html>
    

    As you probably noticed, the name in $_POST['name'] corresponds to the name that we specified in our HTML form.

    Now try uploading the "order.html" and "process.php" files to a PHP enabled server and test them out. If someone selected the item brushes and specified a quantity of 6, then the following would be displayed on "process.php":

    process.php Code:

    You ordered 6 brushes.
    Thank you for ordering from AIT Art Supplies!
    

    PHP & HTML Form Review

    A lot of things were going on in this example. Let us step through it to be sure you understand what was going on.

    1. We first created an HTML form "order.html" that had two input fields specified, "item" and "quantity".
    2. We added two attributes to the form tag to point to "process.php" and set the method to "post".
    3. We had "process.php" get the information that was posted by setting new variables equal to the values in the $_POST associative array.
    4. We used the PHP echo function to output the customers order.

    Remember, this lesson is only to teach you how to use PHP to get information from HTML forms. The example on this page should not be used for a real business.

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  • PHP FUNCTIONS ↓

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    A function is just a name we give to a block of code that can be executed whenever we need it. This might not seem like that big of an idea, but believe me, when you understand and use functions you will be able to save a ton of time and write code that is much more readable!

    For example, you might have a company motto that you have to display at least once on every webpage. If you don't, then you get fired! Well, being the savvy PHP programmer you are, you think to yourself, "this sounds like a situation where I might need functions."

    Tip: Although functions are often thought of as an advanced topic for beginning programmers to learn, if you take it slow and stick with it, functions can be just minor speedbump in your programming career. So don't give up if functions confuse you at first!

    Creating Your First PHP Function

    When you create a function, you first need to give it a name, like myCompanyMotto. It's with this function name that you will be able to call upon your function, so make it easy to type and understand.

    The actual syntax for creating a function is pretty self-explanatory, but you can be the judge of that. First, you must tell PHP that you want to create a function. You do this by typing the keyword function followed by your function name and some other stuff (which we'll talk about later).

    Here is how you would make a function called myCompanyMotto. Note: We still have to fill in the code for myCompanyMotto.

    PHP Code:

    <?php
    function myCompanyMotto(){
    }
    ?>
    

    Note: Your function name can start with a letter or underscore "_", but not a number!

    With a properly formatted function in place, we can now fill in the code that we want our function to execute. Do you see the curly braces in the above example "{ }"? These braces define where our function's code goes. The opening curly brace "{" tells php that the function's code is starting and a closing curly brace "}" tells PHP that our function is done!

    We want our function to print out the company motto each time it's called, so that sounds like it's a job for the echo command!

    PHP Code:

    <?php
    function myCompanyMotto(){
        echo "We deliver quantity, not quality!<br />";
    }
    ?>
    

    That's it! You have written your first PHP function from scratch! Notice that the code that appears within a function is just the same as any other PHP code.

    Using Your PHP Function

    Now that you have completed coding your PHP function, it's time to put it through a test run. Below is a simple PHP script. Let's do two things: add the function code to it and use the function twice.

    PHP Code:

    <?php
    echo "Welcome to AITECHTONIC.com <br />";
    echo "Well, thanks for stopping by! <br />";
    echo "and remember... <br />";
    ?>
    

    PHP Code with Function:

    <?php
    function myCompanyMotto(){
        echo "We deliver quantity, not quality!<br />";
    }
    echo "Welcome to AITECHTONIC.com <br />";
    myCompanyMotto();
    echo "Well, thanks for stopping by! <br />";
    echo "and remember... <br />";
    myCompanyMotto();
    ?>
    

    Display:

    Welcome to AITECHTONIC.com
    We deliver quantity, not quality!
    Well, thanks for stopping by!
    and remember...
    We deliver quantity, not quality!

    Although this was a simple example, it's important to understand that there is a lot going on and there are a lot of areas to make errors. When you are creating a function, follow these simple guidelines:

    • Always start your function with the keyword function
    • Remember that your function's code must be between the "{" and the "}"
    • When you are using your function, be sure you spell the function name correctly
    • Don't give up!

    PHP Functions - Parameters

    Another useful thing about functions is that you can send them information that the function can then use. Our first function myCompanyMotto isn't all that useful because all it does, and ever will do, is print out a single, unchanging string.

    However, if we were to use parameters, then we would be able to add some extra functionality! A parameter appears with the parentheses "( )" and looks just like a normal PHP variable. Let's create a new function that creates a custom greeting based off of a person's name.

    Our parameter will be the person's name and our function will concatenate this name onto a greeting string. Here's what the code would look like.

    PHP Code with Function:

    <?php
    function myGreeting($firstName){
        echo "Hello there ". $firstName . "!<br />";
    }
    ?>
    

    When we use our myGreeting function we have to send it a string containing someone's name, otherwise it will break. When you add parameters, you also add more responsibility to you, the programmer! Let's call our new function a few times with some common first names.

    PHP Code:

    <?php
    function myGreeting($firstName){
        echo "Hello there ". $firstName . "!<br />";
    }
    myGreeting("Jack");
    myGreeting("Ahmed");
    myGreeting("Julie");
    myGreeting("Charles");
    ?>
    

    Display:

    Hello there Jack!
    Hello there Ahmed!
    Hello there Julie!
    Hello there Charles!

    It is also possible to have multiple parameters in a function. To separate multiple parameters PHP uses a comma ",". Let's modify our function to also include last names.

    PHP Code:

    <?php
    function myGreeting($firstName, $lastName){
        echo "Hello there ". $firstName ." ". $lastName ."!<br />";
    }
    myGreeting("Jack", "Black");
    myGreeting("Ahmed", "Zewail");
    myGreeting("Julie", "Roberts");
    myGreeting("Charles", "Schwab");
    ?>
    

    Display:

    Hello there Jack Black!
    Hello there Ahmed Zewail!
    Hello there Julie Roberts!
    Hello there Charles Schwab!

    PHP Functions - Returning Values

    Besides being able to pass functions information, you can also have them return a value. However, a function can only return one thing, although that thing can be any integer, float, array, string, etc. that you choose!

    How does it return a value though? Well, when the function is used and finishes executing, it sort of changes from being a function name into being a value. To capture this value you can set a variable equal to the function. Something like:

    • $myVar = somefunction();

    Let's demonstrate this returning of a value by using a simple function that returns the sum of two integers.

    PHP Code:

    <?php
    function mySum($numX, $numY){
        $total = $numX + $numY;
        return $total; 
    }
    $myNumber = 0;
    echo "Before the function, myNumber = ". $myNumber ."<br />";
    $myNumber = mySum(3, 4); // Store the result of mySum in $myNumber
    echo "After the function, myNumber = " . $myNumber ."<br />";
    ?>
    

    Display:

    Before the function, myNumber = 0
    After the function, myNumber = 7

    When we first print out the value of $myNumber it is still set to the original value of 0. However, when we set $myNumber equal to the function mySum, $myNumber is set equal to mySum's result. In this case, the result was 3 + 4 = 7, which was successfully stored into $myNumber and displayed in the second echo statement!

    PHP Functions - Practice Makes Perfect

    If you are new to programming, then this lesson might or might not seem like overkill. If you are having a hard time understanding lessons, the best piece of advice would be to do your best the first time, then be sure to come back tomorrow and next week and see if it makes anymore sense. Chances are, after going through this tutorial more than once, with breaks in between, this topic will be mastered.

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  • PHP POST & GET ↓

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    Recall from the PHP Forms Lesson where we used an HTML form and sent it to a PHP web page for processing. In that lesson we opted to use the the post method for submitting, but we could have also chosen the get method. This lesson will review both transferring methods.

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    POST - Review

    In our PHP Forms Lesson we used the post method. This is what the pertinent line of HTML code looked like:

    HTML Code Excerpt:

    <form action="process.php" method="post">
    <select name="item">
    ...
    <input name="quantity" type="text" />
    

    This HTML code specifies that the form data will be submitted to the "process.php" web page using the POST method. The way that PHP does this is to store all the "posted" values into an associative array called "$_POST". Be sure to take notice the names of the form data names, as they represent the keys in the "$_POST" associative array.

    Now that you know about associative arrays, the PHP code from "process.php" should make a litte more sense.

    PHP Code Excerpt:

    $quantity = $_POST['quantity'];
    $item = $_POST['item'];
    

    The form names are used as the keys in the associative array, so be sure that you never have two input items in your HTML form that have the same name. If you do, then you might see some problems arise.

    PHP - GET

    As we mentioned before, the alternative to the post method is get. If we were to change our HTML form to the get method, it would look like this:

    HTML Code Excerpt:

    <form action="process.php" method="get">
    <select name="item">
    ...
    <input name="quantity" type="text" />
    

    The get method is different in that it passes the variables along to the "process.php" web page by appending them onto the end of the URL. The URL, after clicking submit, would have this added on to the end of it:

    "?item=##&quantity=##"

    The question mark "?" tells the browser that the following items are variables. Now that we changed the method of sending information on "order.html", we must change the "process.php" code to use the "$_GET" associative array.

    PHP Code Excerpt:

    $quantity = $_GET['quantity'];
    $item = $_GET['item'];
    

    After changing the array name the script will function properly. Using the get method displays the variable information to your visitor, so be sure you are not sending password information or other sensitive items with the get method. You would not want your visitors seeing something they are not supposed to!

    Security Precautions

    Whenever you are taking user input and using you need to be sure that the input is safe. If you are going to insert the data into a MySQL database, then you should be sure you have thought about preventing MySQL Injection. If you are going to make a user's input available to the public, then you should think about PHP htmlentities.

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  • PHP MAGIC QUOTES ↓

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    Prior to PHP 6 there was a feature called magic quotes that was created to help protect newbie programmers from writing bad form processing code. Magic quotes would automatically escape risky form data that might be used for SQL Injection with a backslash \. The characters escaped by PHP include: quote ', double quote ", backslash \ and NULL characters.

    However, this newbie protection proved to cause more problems than it solved and is not in PHP 6. If your PHP version is any version before 6 then you should use this lesson to learn more about how magic quotes can affect you.

    Magic Quotes - Are They Enabled?

    First things first, you need to check to see if you have magic quotes enabled on you server. The get_magic_quotes_gpc function will return a 0 (off) or a 1 (on). These boolean values will fit nicely into an if statement where 1 is true and 0 is false.

    PHP Code:

    if(get_magic_quotes_gpc())
    	echo "Magic quotes are enabled";
    else
    	echo "Magic quotes are disabled";
    

    Display:

    Magic quotes are enabled

    If you received the message "Magic quotes are enabled" then you should definitely continue reading this lesson, if not feel free to learn about it in case you are developing for servers that might have quotes on or off.

    Magic Quotes in Action

    Now lets make a simple form processor to show how machines with magic quotes enabled will escape those potentially risky characters. This form submits to itself, so you only need to make one file, "magic-quotes.php" to test it out.

    magic-quotes.php Code:

    <?php
    echo "Altered Text: ".$_POST['question'];
    ?>
    
    <form method='post'>
    Question: <input type='text' name='question'/><br />
    <input type='submit'>
    
    </form>
    

    This simple form will display to you what magic quotes is doing. If you were to enter and submit the string: Sandy said, "It's a beautiful day outside and I like to use \'s." You would receive the following output.

    Display:

    Altered Text: Sandy said, \"It\'s a beautiful day outside and I like to use \\\'s.\"
    Question:

    Magic quotes did a number on that string, didn't it? Notice that there is a backslash before all of those risky characters we talked about earlier. After magic quotes:

    • A backslash \ becomes \\
    • A quote ' becomes \'
    • A double-quote " becomes \"

    Now say that you wanted to remove the escaping that magic quotes puts in, you have two options: disable magic quotes or strip the backslashes magic quotes adds.

    Removing Backslashes - stripslashes()

    Before you use PHP's backslash removal function stripslashes it's smart to add some magic quote checking like our "Are They Enabled?" section above. This way you won't accidentally be removing slashes that are legitimate in the future if your PHP's magic quotes setting changes in the future.

    magic-quotes.php Code:

    <?php
    echo "Removed Slashes: ";
    // Remove those slashes
    if(get_magic_quotes_gpc())
    	echo stripslashes($_POST['question']);
    else
    	echo $_POST['question'];
    	
    ?>
    
    <form method='post'>
    Question: <input type='text' name='question'/><br />
    <input type='submit'>
    
    </form>
    

    Our new output for our string containing risky characters would now be:

    Display:

    Removed Slashes: Sandy said, "It's a beautiful day outside and I like to use \'s."
    Question:
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  • PHP HTMLENTITIES FUNCTION ↓

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    Whenever you allow your users to submit text to your website, you need to be careful that you don't leave any security holes open for malicious users to exploit. If you are ever going to allow user submitted text to be visible by the public you should consider using the htmlentities function to prevent them from running html code and scripts that may be harmful to your visitors.

    PHP - Converting HTML into Entities

    The htmlentities function takes a string and returns the same string with HTML converted into HTML entities. For example, the string "<script>" would be converted to "&lt;script&gt;".

    By converting the < and > into entities, it prevents the browser from using it as an HTML element and it prevents the code from running if you were to display some user's input on your website.

    This may seem a little complicated, but if you think of the way a browser works, in separate stages, it becomes a little easier. Let's look at the way the function htmlentities changes the data at three different levels: in PHP, in raw HTML and in the web browser. The sample string is a bad script that will redirect visitors to the malicious user's own website.

    PHP Code:

    // An imaginary article submission from a bad user
    //  it will redirect anyone to example.com if the code is run in a browser
    $userInput = "I am going to hax0r your site, hahaha!
    	<script type='text/javascript'>
    	window.location = 'http://www.example.com/'
    	</script>'";
    	
    //Lets make it safer before we use it
    $userInputEntities = htmlentities($userInput);
    
    //Now we can display it
    echo $userInputEntities;
    

    The HTML output of the above script would be as follows:

    Safe Raw HTML Code:

    I am going to hax0r your site, hahaha!
    	&lt;script type='text/javascript'&gt;
    	window.location = 'http://www.example.com/'
    	&lt;/script&gt;'
    

    If we had not used htmlentities to convert any HTML code into safe entities, this is what the raw HTML code would be and it would have redirect a visitor to example.com.

    Dangerous Raw HTML Code:

    I am going to hax0r your site, hahaha!
    	<script type='text/javascript'>
    	window.location = 'http://www.example.com/'
    	</script>'
    

    Those two HTML code examples are what you would see if you were to view source on the web page. However, if you were just viewing the output normally in your browser you would see the following.

    Safe Display:

    I am going to hax0r your site, hahaha! <script type='text/javascript'> window.location = 'http://www.example.com/' </script>'

    Dangerous Display:

    You'd see whatever spammer site that the malicious user had sent you to. Probably some herbal supplement site or weight loss pills would be displayed.

    When Would You Use htmlentities?

    Anytime you allow users to submit content to your website, that other visitors can see, you should consider removing the ability to let them use HTML. Although this will remove a lot of cool things that your users can do, like making heavily customized content, it will prevent your site from a lot of common attacks. With some custom coding you can just remove specific tags from running, but that is beyond the scope of this lesson.

    Just remember, that when allowing users to submit content to your site you are also giving them access to your website. Be sure you take the proper precautions.

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  • PHP FILEUPLOADING ↓

    A PHP script can be used with a HTML form to allow users to upload files to the server. Initially files are uploaded into a temporary directory and then relocated to a target destination by a PHP script.

    Information in the phpinfo.php page describes the temporary directory that is used for file uploads as upload_tmp_dir and the maximum permitted size of files that can be uploaded is stated as upload_max_filesize. These parameters are set into PHP configuration file php.ini

    The process of uploading a file follows these steps −

    • The user opens the page containing a HTML form featuring a text files, a browse button and a submit button.

    • The user clicks the browse button and selects a file to upload from the local PC.

    • The full path to the selected file appears in the text filed then the user clicks the submit button.

    • The selected file is sent to the temporary directory on the server.

    • The PHP script that was specified as the form handler in the form's action attribute checks that the file has arrived and then copies the file into an intended directory.

    • The PHP script confirms the success to the user.

    As usual when writing files it is necessary for both temporary and final locations to have permissions set that enable file writing. If either is set to be read-only then process will fail.

    An uploaded file could be a text file or image file or any document.

    Creating an upload form

    The following HTM code below creates an uploader form. This form is having method attribute set to post and enctype attribute is set to multipart/form-data

    <?php
       if(isset($_FILES['image'])){
          $errors= array();
          $file_name = $_FILES['image']['name'];
          $file_size =$_FILES['image']['size'];
          $file_tmp =$_FILES['image']['tmp_name'];
          $file_type=$_FILES['image']['type'];
          $file_ext=strtolower(end(explode('.',$_FILES['image']['name'])));
          
          $expensions= array("jpeg","jpg","png");
          
          if(in_array($file_ext,$expensions)=== false){
             $errors[]="extension not allowed, please choose a JPEG or PNG file.";
          }
          
          if($file_size > 2097152){
             $errors[]='File size must be excately 2 MB';
          }
          
          if(empty($errors)==true){
             move_uploaded_file($file_tmp,"images/".$file_name);
             echo "Success";
          }
          else{
             print_r($errors);
          }
       }
    ?>
    <html>
       <body>
          
          <form action="" method="POST" enctype="multipart/form-data">
             <input type="file" name="image" />
             <input type="submit"/>
          </form>
          
       </body>
    </html>
    

    Creating an upload script

    There is one global PHP variable called $_FILES. This variable is an associate double dimension array and keeps all the information related to uploaded file. So if the value assigned to the input's name attribute in uploading form was file, then PHP would create following five variables −

    • $_FILES['file']['tmp_name'] − the uploaded file in the temporary directory on the web server.

    • $_FILES['file']['name'] − the actual name of the uploaded file.

    • $_FILES['file']['size'] − the size in bytes of the uploaded file.

    • $_FILES['file']['type'] − the MIME type of the uploaded file.

    • $_FILES['file']['error'] − the error code associated with this file upload.

    Example

    Below example should allow upload images and gives back result as uploaded file information.

    <?php
       if(isset($_FILES['image'])){
          $errors= array();
          $file_name = $_FILES['image']['name'];
          $file_size =$_FILES['image']['size'];
          $file_tmp =$_FILES['image']['tmp_name'];
          $file_type=$_FILES['image']['type'];
          $file_ext=strtolower(end(explode('.',$_FILES['image']['name'])));
          
          $expensions= array("jpeg","jpg","png");
          
          if(in_array($file_ext,$expensions)=== false){
             $errors[]="extension not allowed, please choose a JPEG or PNG file.";
          }
          
          if($file_size > 2097152){
             $errors[]='File size must be excately 2 MB';
    		}
          
          if(empty($errors)==true){
             move_uploaded_file($file_tmp,"images/".$file_name);
             echo "Success";
          }
          else{
             print_r($errors);
          }
       }
    ?>
    <html>
       <body>
          
          <form action="" method="POST" enctype="multipart/form-data">
             <input type="file" name="image" />
             <input type="submit"/>
    			
             <ul>
                <li>Sent file: <?php echo $_FILES['image']['name'];  ?>
                <li>File size: <?php echo $_FILES['image']['size'];  ?>
                <li>File type: <?php echo $_FILES['image']['type'] ?>
             </ul>
    			
          </form>
          
       </body>
    </html>
    
  • PHP FILES (Create, Open, Close, Write etc. ↓

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    Manipulating files is a basic necessity for serious programmers and PHP gives you a great deal of tools for creating, uploading, and editing files.

    This section of the PHP tutorial is completely dedicated to how PHP can interact with files. After completing this section you should have a solid understanding of all types of file manipulation in PHP!

    PHP - Files: Be Careful

    When you are manipulating files you must be very careful because you can do a lot of damage if you do something wrong. Common errors include editing the wrong file, filling a hard-drive with garbage data, and accidentally deleting a file's contents.

    It is our hope that you will be able to avoid these and other slipups after reading this tutorial. However, we know that there are so many places where code can take a wrong turn, so we urge you to take extra care when dealing with files in PHP.

    PHP - Files: Overview

    The presentation of the file lessons will begin with how to create, open, and close a file. After establishing those basics, we will then cover other important file tasks, such as: read, write, append, truncate, and uploading files with PHP.

    PHP - File Create

    Before you can do anything with a file it has to exist! In this lesson you will learn how to create a file using PHP.

    PHP - Creating Confusion

    In PHP, a file is created using a command that is also used to open files. It may seem a little confusing, but we'll try to clarify this conundrum.

    In PHP the fopen function is used to open files. However, it can also create a file if it does not find the file specified in the function call. So if you use fopen on a file that does not exist, it will create it, given that you open the file for writing or appending (more on this later).

    PHP - How to Create a File

    The fopen function needs two important pieces of information to operate correctly. First, we must supply it with the name of the file that we want it to open. Secondly, we must tell the function what we plan on doing with that file (i.e. read from the file, write information, etc).

    Since we want to create a file, we must supply a file name and tell PHP that we want to write to the file. Note: We have to tell PHP we are writing to the file, otherwise it will not create a new file.

    PHP Code:

    $ourFileName = "testFile.txt";
    $ourFileHandle = fopen($ourFileName, 'w') or die("can't open file");
    fclose($ourFileHandle);
    

    The file "testFile.txt" should be created in the same directory where this PHP code resides. PHP will see that "testFile.txt" does not exist and will create it after running this code. There's a lot of information in those three lines of code, let's make sure you understand it.

    1. $ourFileName = "testFile.txt";

      Here we create the name of our file, "testFile.txt" and store it into a PHP String variable $ourFileName.

    2. $ourFileHandle = fopen($ourFileName, 'w') or die("can't open file");

      This bit of code actually has two parts. First we use the function fopen and give it two arguments: our file name and we inform PHP that we want to write by passing the character "w".

      Second, the fopen function returns what is called a file handle, which will allow us to manipulate the file. We save the file handle into the $ourFileHandle variable. We will talk more about file handles later on.

    3. fclose($ourFileHandle);

      We close the file that was opened. fclose takes the file handle that is to be closed. We will talk more about this more in the file closing lesson.

    PHP - Permissions

    If you are trying to get this program to run and you are having errors, you might want to check that you have granted your PHP file access to write information to the hard drive. Setting permissions is most often done with the use of an FTP program to execute a command called CHMOD. Use CHMOD to allow the PHP file to write to disk, thus allowing it to create a file.

    In the near future AITECHTONIC.com will have a more in-depth tutorial on how to use CHMOD to set file permissions.

    PHP - File Open

    In the previous lesson we used the function fopen to create a new file. In this lesson we will be going into the details of this important function and see what it has to offer.

    PHP - Different Ways to Open a File

    For many different technical reasons, PHP requires you to specify your intentions when you open a file. Below are the three basic ways to open a file and the corresponding character that PHP uses.

    • Read: 'r'

    Open a file for read only use. The file pointer begins at the front of the file.

    • Write: 'w'

    Open a file for write only use. In addition, the data in the file is erased and you will begin writing data at the beginning of the file. This is also called truncating a file, which we will talk about more in a later lesson. The file pointer begins at the start of the file.

    • Append: 'a'

    Open a file for write only use. However, the data in the file is preserved and you begin will writing data at the end of the file. The file pointer begins at the end of the file.

    A file pointer is PHP's way of remembering its location in a file. When you open a file for reading, the file pointer begins at the start of the file. This makes sense because you will usually be reading data from the front of the file.

    However, when you open a file for appending, the file pointer is at the end of the file, as you most likely will be appending data at the end of the file. When you use reading or writing functions they begin at the location specified by the file pointer.

    PHP - Explanation of Different Types of fopen

    These three basic ways to open a file have distinct purposes. If you want to get information out of a file, like search an e-book for the occurrences of "cheese", then you would open the file for read only.

    If you wanted to write a new file, or overwrite an existing file, then you would want to open the file with the "w" option. This would wipe clean all existing data within the file.

    If you wanted to add the latest order to your "orders.txt" file, then you would want to open it to append the data on to the end. This would be the "a" option.

    PHP - File Open: Advanced

    There are additional ways to open a file. Above we stated the standard ways to open a file. However, you can open a file in such a way that reading and writing is allowable! This combination is done by placing a plus sign "+" after the file mode character.

    • Read/Write: 'r+'

    Opens a file so that it can be read from and written to. The file pointer is at the beginning of the file.

    • Write/Read: 'w+'

    This is exactly the same as r+, except that it deletes all information in the file when the file is opened.

    • Append: 'a+'

    This is exactly the same as r+, except that the file pointer is at the end of the file.

    PHP - File Open: Cookie Cutter

    Below is the correct form for opening a file with PHP. Replace the (X) with one of the options above (i.e. r, w, a, etc).

    Pseudo PHP Code:

    $ourFileName = "testFile.txt";
    $fh = fopen($ourFileName, 'X') or die("Can't open file");
    fclose($fh);
    

    PHP - File Open: Summary

    You can open a file in many different ways. You can delete everything and begin writing on a clean slate, you can add to existing data, and you can simply read information from a file. In later lessons we will go into greater detail on how each of these different ways to open a file is used in the real world and give some helpful examples.

    PHP - File Close

    The next logical step after you have opened a file and finished your business with it is to close that file down. You don't want an open file running around on your server taking up resources and causing mischief!

    PHP - File Close Description

    In PHP it is not system critical to close all your files after using them because the server will close all files after the PHP code finishes execution. However the programmer is still free to make mistakes (i.e. editing a file that you accidentally forgot to close). You should close all files after you have finished with them because it's a good programming practice and because we told you to!

    PHP - File Close Function

    In a previous tutorial, we had a call to the function fclose to close down a file after we were done with it. Here we will repeat that example and discuss the importance of closing a file.

    PHP Code:

    $ourFileName = "testFile.txt";
    $ourFileHandle = fopen($ourFileName, 'w') or die("can't open file");
    fclose($ourFileHandle);
    

    The function fclose requires the file handle that we want to close down. In our example we set our variable "$fileHandle" equal to the file handle returned by the fopen function.

    After a file has been closed down with fclose it is impossible to read, write or append to that file unless it is once more opened up with the fopen function.

    PHP - File Write

    Now that you know how to open and close a file, lets get on to the most useful part of file manipulation, writing! There is really only one main function that is used to write and it's logically called fwrite.

    PHP - File Open: Write

    Before we can write information to our test file we have to use the function fopen to open the file for writing.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'w');
    

    PHP - File Write: fwrite Function

    We can use php to write to a text file. The fwrite function allows data to be written to any type of file. Fwrite's first parameter is the file handle and its second parameter is the string of data that is to be written. Just give the function those two bits of information and you're good to go!

    Below we are writing a couple of names into our test file testFile.txt and separating them with a carriaged return.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'w') or die("can't open file");
    $stringData = "Bobby Bopper\n";
    fwrite($fh, $stringData);
    $stringData = "Tracy Tanner\n";
    fwrite($fh, $stringData);
    fclose($fh);
    

    The $fh variable contains the file handle for testFile.txt. The file handle knows the current file pointer, which for writing, starts out at the beginning of the file.

    We wrote to the file testFile.txt twice. Each time we wrote to the file we sent the string $stringData that first contained Bobby Bopper and second contained Tracy Tanner. After we finished writing we closed the file using the fclose function.

    If you were to open the testFile.txt file in NOTEPAD it would look like this:

    Contents of the testFile.txt File:

    Bobby Bopper
    Tracy Tanner

    PHP - File Write: Overwriting

    Now that testFile.txt contains some data we can demonstrate what happens when you open an existing file for writing. All the data contained in the file is wiped clean and you start with an empty file. In this example we open our existing file testFile.txt and write some new data into it.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'w') or die("can't open file");
    $stringData = "Floppy Jalopy\n";
    fwrite($fh, $stringData);
    $stringData = "Pointy Pinto\n";
    fwrite($fh, $stringData);
    fclose($fh);
    

    If you now open the testFile.txt file you will see that Bobby and Tracy have both vanished, as we expected, and only the data we just wrote is present.

    Contents of the testFile.txt File:

    Floppy Jalopy
    Pointy Pinto

    In the next lesson we will show you how to get information out of a file by using PHP's read data functions!

    PHP - File Open: Read

    Before we can read information from a file we have to use the function fopen to open the file for reading. Here's the code to read-open the file we created in the PHP File Write lessons.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'r');
    

    The file we created in the last lesson was named "testFile.txt". Your PHP script that you are writing should reside in the same directory as "text.txt". Here are the contents of our file from File Write.

    testFile.txt Contents:

    Floppy Jalopy
    Pointy Pinto

    Now that the file is open, with read permissions enabled, we can get started!

    PHP - File Read: fread Function

    The fread function is the staple for getting data out of a file. The function requires a file handle, which we have, and an integer to tell the function how much data, in bytes, it is supposed to read.

    One character is equal to one byte. If you wanted to read the first five characters then you would use five as the integer.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'r');
    $theData = fread($fh, 5);
    fclose($fh);
    echo $theData;
    

    Display:

    Flopp

    The first five characters from the testFile.txt file are now stored inside $theData. You could echo this string, $theData, or write it to another file.

    If you wanted to read all the data from the file, then you need to get the size of the file. The filesize function returns the length of a file, in bytes, which is just what we need! The filesize function requires the name of the file that is to be sized up.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'r');
    $theData = fread($fh, filesize($myFile));
    fclose($fh);
    echo $theData;
    

    Display:

    Floppy Jalopy Pointy Pinto

    Note: It is all on one line because our "testFile.txt" file did not have a <br /> tag to create an HTML line break. Now the entire contents of the testFile.txt file is stored in the string variable $theData.

    PHP - File Read: gets Function

    PHP also lets you read a line of data at a time from a file with the gets function. This can or cannot be useful to you, the programmer. If you had separated your data with new lines then you could read in one segment of data at a time with the gets function.

    Lucky for us our "testFile.txt" file is separated by new lines and we can utilize this function.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'r');
    $theData = fgets($fh);
    fclose($fh);
    echo $theData;
    

    testFile.txt Contents:

    Floppy Jalopy

    The fgets function searches for the first occurrence of "\n" the newline character. If you did not write newline characters to your file as we have done in File Write, then this function might not work the way you expect it to.

    PHP - File Delete

    You know how to create a file. You know how to open a file in an assortment of different ways. You even know how to read and write data from a file!

    Now it's time to learn how to destroy (delete) files. In PHP you delete files by calling the unlink function.

    PHP - File Unlink

    When you view the contents of a directory you can see all the files that exist in that directory because the operating system or application that you are using displays a list of filenames. You can think of these filenames as links that join the files to the directory you are currently viewing.

    If you unlink a file, you are effectively causing the system to forget about it or delete it!

    Before you can delete (unlink) a file, you must first be sure that it is not open in your program. Use the fclose function to close down an open file.

    PHP - Unlink Function

    Remember from the PHP File Create lesson that we created a file named testFile.txt.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'w') or die("can't open file");
    fclose($fh);
    

    Now to delete testFile.txt we simply run a PHP script that is located in the same directory. Unlink just needs to know the name of the file to start working its destructive magic.

    PHP Code:

    $myFile = "testFile.txt";
    unlink($myFile);
    

    The testFile.txt should now be removed.

    PHP - Unlink: Safety First!

    With great power comes a slough of potential things you can mess up! When you are performing the unlink function be sure that you are deleting the right file!

    PHP - File Open: Append

    If we want to add on to a file we need to open it up in append mode. The code below does just that.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'a');
    

    If we were to write to the file it would begin writing data at the end of the file.

    PHP - File Write: Appending Data

    Using the testFile.txt file we created in the File Write lesson , we are going to append on some more data.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'a') or die("can't open file");
    $stringData = "New Stuff 1\n";
    fwrite($fh, $stringData);
    $stringData = "New Stuff 2\n";
    fwrite($fh, $stringData);
    fclose($fh);
    

    You should noticed that the way we write data to the file is exactly the same as in the Write lesson. The only thing that is different is that the file pointer is placed at the end of the file in append mode, so all data is added to the end of the file.

    The contents of the file testFile.txt would now look like this:

    Contents of the testFile.txt File:

    Floppy Jalopy
    Pointy Pinto
    New Stuff 1
    New Stuff 2

    PHP - Append: Why Use It?

    The above example may not seem very useful, but appending data onto a file is actually used everyday. Almost all web servers have a log of some sort. These various logs keep track of all kinds of information, such as: errors, visitors, and even files that are installed on the machine.

    A log is basically used to document events that occur over a period of time, rather than all at once. Logs: a perfect use for append!

    PHP - File Truncate

    As we have mentioned before, when you open a file for writing with the paramater 'w' it completely wipes all data from that file. This action is also referred to as "truncating" a file. Truncate literally means to shorten.

    PHP - File Open: Truncate

    To erase all the data from our testFile.txt file we need to open the file for normal writing. All existing data within testFile.txt will be lost.

    PHP Code:

    $myFile = "testFile.txt";
    $fh = fopen($myFile, 'w');
    fclose($fh);
    

    PHP - Truncate: Why Use It?

    Truncating is most often used on files that contain data that will only be used for a short time, before needing to be replaced. These type of files are most often referred to as temporary files.

    For example, you could create an online word processor that automatically saves every thirty seconds. Every time it saves it would take all the data that existed within some HTML form text box and save it to the server. This file, say tempSave.txt, would be truncated and overwritten with new, up-to-date data every thirty seconds.

    This might not be the most efficient program, but it is a nice usage of truncate.

    PHP - File Upload

    A very useful aspect of PHP is its ability to manage file uploads to your server. Allowing users to upload a file to your server opens a whole can of worms, so please be careful when enabling file uploads.

    PHP - File Upload: HTML Form

    Before you can use PHP to manage your uploads, you must first build an HTML form that lets users select a file to upload. See our HTML Form lesson for a more in-depth look at forms.

    HTML Code:

    <form enctype="multipart/form-data" action="uploader.php" method="POST">
    <input type="hidden" name="MAX_FILE_SIZE" value="100000" />
    Choose a file to upload: <input name="uploadedfile" type="file" /><br />
    <input type="submit" value="Upload File" />
    </form>
    

    Here is a brief description of the important parts of the above code:

    • enctype="multipart/form-data" - Necessary for our to-be-created PHP file to function properly.
    • action="uploader.php" - The name of our PHP page that will be created, shortly.
    • method="POST" - Informs the browser that we want to send information to the server using POST.
    • input type="hidden" name="MA... - Sets the maximum allowable file size, in bytes, that can be uploaded. This safety mechanism is easily bypassed and we will show a solid backup solution in PHP. We have set the max file size to 100KB in this example.
    • input name="uploadedfile" - uploadedfile is how we will access the file in our PHP script.

    Save that form code into a file and call it upload.html. If you view it in a browser it should look like this:

    Display:

    Choose a file to upload:

    After the user clicks submit, the data will be posted to the server and the user will be redirected to uploader.php. This PHP file is going to process the form data and do all the work.

    PHP - File Upload: What's the PHP Going to Do?

    Now that we have the right HTML form we can begin to code the PHP script that is going to handle our uploads. Typically, the PHP file should make a key decision with all uploads: keep the file or throw it away. A file might be thrown away from many reasons, including:

    • The file is too large and you do not want to have it on your server.
    • You wanted the person to upload a picture and they uploaded something else, like an executable file (.exe).
    • There were problems uploading the file and so you can't keep it.

    This example is very simple and omits the code that would add such functionality.

    PHP - File Upload: uploader.php

    When the uploader.php file is executed, the uploaded file exists in a temporary storage area on the server. If the file is not moved to a different location it will be destroyed! To save our precious file we are going to need to make use of the $_FILES associative array.

    The $_FILES array is where PHP stores all the information about files. There are two elements of this array that we will need to understand for this example.

    • uploadedfile - uploadedfile is the reference we assigned in our HTML form. We will need this to tell the $_FILES array which file we want to play around with.
    • $_FILES['uploadedfile']['name'] - name contains the original path of the user uploaded file.
    • $_FILES['uploadedfile']['tmp_name'] - tmp_name contains the path to the temporary file that resides on the server. The file should exist on the server in a temporary directory with a temporary name.

    Now we can finally start to write a basic PHP upload manager script! Here is how we would get the temporary file name, choose a permanent name, and choose a place to store the file.

    PHP Code:

    // Where the file is going to be placed 
    $target_path = "uploads/";
    
    /* Add the original filename to our target path.  
    Result is "uploads/filename.extension" */
    $target_path = $target_path . basename( $_FILES['uploadedfile']['name']); 
    

    NOTE: You will need to create a new directory in the directory where uploader.php resides, called "uploads", as we are going to be saving files there.

    We now have all we need to successfully save our file to the server. $target_path contains the path where we want to save our file to.

    PHP - File Upload: move_uploaded_file Function

    Now all we have to do is call the move_uploaded_file function and let PHP do its magic. The move_uploaded_file function needs to know 1) The path of the temporary file (check!) 2) The path where it is to be moved to (check!).

    PHP Code:

    $target_path = "uploads/";
    
    $target_path = $target_path . basename( $_FILES['uploadedfile']['name']); 
    
    if(move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) {
        echo "The file ".  basename( $_FILES['uploadedfile']['name']). 
        " has been uploaded";
    } else{
        echo "There was an error uploading the file, please try again!";
    }
    

    If the upload is successful, then you will see the text "The file filename has been uploaded". This is because move_uploaded_file returns true if the file was moved, and false if it had a problem.

    If there was a problem then the error message "There was an error uploading the file, please try again!" would be displayed.

    PHP - File Upload: Safe Practices!

    Note: This script is for education purposes only. We do not recommend placing this on a web page viewable to the public.

    These few lines of code we have given you will allow anyone to upload data to your server. Because of this, we recommend that you do not have such a simple file uploader available to the general public. Otherwise, you might find that your server is filled with junk or that your server's security has been compromised.

    We hope you enjoyed learning about how to work with uploading files with PHP. In the near future we will be adding an advanced lesson that will include more security and additional features!

    advertise here!!!
  • PHP STRING ↓

    advertise here!!!

    PHP - String Position - strpos

    Being able to manipulate strings is a valuable skill, especially in PHP. You'll most likely come across a programming problem that requires you to find some data in a string. The beginning of a lot of your string manipulation expertise will begin with the strpos function, which allows you to find data in your string.

    Searching a String with strpos

    The way strpos works is it takes some string you want to search in as its first argument and another string, which is what you are actually searching for, as the second argument. If the function can find a search match, then it will return the position of the first match. However, if it can't find a match it will return false.

    To make this function crystal clear, lets search a numbered, in-order string, for the number five.

    PHP Code:

    $numberedString = "1234567890"; // 10 numbers from 1 to 0
    
    $fivePos = strpos($numberedString, "5");
    echo "The position of 5 in our string was $fivePos";
    

    Display:

    The position of 5 in our string was 4

    Notice that the position is 4, which may seem confusing at first, until you realize that PHP starts counting from 0.

    • The number 1 - Position 0 - No match
    • The number 2 - Position 1 - No match
    • The number 3 - Position 2 - No match
    • The number 4 - Position 3 - No match
    • The number 5 - Position 4 - Match

    Although we only searched for a single character, you can use this function to search for a string with any number of characters. Also, it is important to note that this function will return the position of the start of the first match. So if we had searched the same string for "567890" we would again find a match and position 4 because that is where the match starts.

    Finding All Occurrences in a String with Offset

    One of the limitations of strpos is that it only returns the position of the very first match. If there are 5,000 other matches in the string you would be none the wiser, unless you take action!

    There is a third (optional) argument to strpos that will let you specify where to begin your search of the string. If you were to store the position of the last match and use that + 1 as an offset, you would skip over the first match and be find the next one.

    PHP Code:

    $numberedString = "1234567890123456789012345678901234567890";
    
    $fivePos = strpos($numberedString, "5");
    echo "The position of 5 in our string was $fivePos";
    $fivePos2 = strpos($numberedString, "5", $fivePos + 1);
    echo "<br />The position of the second 5 was $fivePos2";
    

    Display:

    The position of 5 in our string was 4
    The position of the second 5 was 14

    By taking the first match's position of 4 and adding 1 we then asked strpos to begin searching after the last match. The string it was actually searching after computing the offset was: 6789012345... Letting us find the second 5 in the string.

    If we use our knowledge of PHP While Loops we can find every single 5 in our string numberedString with just a few lines of code.

    PHP Code:

    $numberedString = "1234567890123456789012345678901234567890";
    $offset = 0; // initial offset is 0
    $fiveCounter = 0;
    
    // First check if there is a "5" at position 0.
    if(strpos($numberedString, "5") == 0){
    	$fiveCounter++;
    	echo "<br />Five #$fiveCounter is at position - 0";
    }
    
    // Check the rest of the string for 5's
    while($offset = strpos($numberedString, "5", $offset + 1)){
    	$fiveCounter++;
    	echo "<br />Five #$fiveCounter is at position - $offset";
    }
    

    Display:

    Five #1 is at position - 4
    Five #2 is at position - 14
    Five #3 is at position - 24
    Five #4 is at position - 34

    That conditional statement in our while loop may look a little intimidating, but not if you break it down.

    • $offset = strpos($numberedString, "5", $offset + 1) - This is our conditional statement for our PHP While Loop. If this ever is false the while loop will stop running. This conditional statement always runs before each pass through the while loop.
    • strpos($numberedString, "5", $offset + 1) - This is the same code we used in a previous example. We are going to search our string numberedString for the number 5 and use the last match's value (stored in $offset) + 1 to skip over the last match. The first $offset we use has a value of 0, so that we start at the beginning of the string.
    • $offset = strpos(... We are going to store the location returned by strpos into $offset so that we can skip this match the next time the while loop runs through the code. If strpos ever fails to find a match then this will be set to false making our while loop stop executing.

    PHP str_replace Function

    Another key tool to have in your programming toolbox is the ability to quickly replace parts of a PHP string with new values. The str_replace function is similar to a word processor's "Replace All" command that lets you specify a word and what to replace it with, then replaces every occurrence of that word in the document.

    str_replace Parameters

    str_replace has three parameters that are required for the function to work properly. str_replace(search, replace, originalString).

    1. search - This is what you want to search your string for. This can be a string or an array.
    2. replace - All matches for search will be replaced with this value. This can be a string or an array.
    3. originalString - This is what search and replace will be operating on. The str_replace function will return a modified version of originalString when it completes.

    str_replace Simple Example

    Imagine we are working at a school district and need to create a webpage for the students' parents. The webpage has an introduction string that we need to customize depending on if the student is male or female. With str_replace this is mighty easy.

    PHP Code:

    //string that needs to be customized
    $rawstring = "Welcome Birmingham parents. Your replaceme is a pleasure to have!";
    
    //male string
    $malestr = str_replace("replaceme", "son", $rawstring);
    
    //female string
    $femalestr = str_replace("replaceme", "daughter", $rawstring);
    
    echo "Son: ". $malestr . "<br />";
    echo "Daughter: ". $femalestr;
    

    Display:

    Son: Welcome Birmingham parents. Your son is a pleasure to have!
    Daughter: Welcome Birmingham parents. Your daughter is a pleasure to have!

    With these two gender customized strings created we could then provide a more engaging experience for the student's parents when they logged into the school website with their kid's credentials.

    str_replace Arrays: Multiple Replaces in One

    In the last example we only needed to replace one word replaceme in our string, but what if we wanted to replace many words? We could just use the function multiple times to get the job done, or we could create an array of placeholders and a second array of replace values to get it all done in one function call.

    The key thing to understand with this technique is that you are creating two arrays that will be used to swap values. The first item in placeholders will be replaced by the first item in the replace values, the second item of placeholders replaced with the second in replace values and so on and so forth.

    Let's extend our simple example to be a complete form letter addressed to a student's parents.

    PHP Code:

    //string that needs to be customized
    $rawstring = "Welcome Birmingham parent! <br />
    	Your offspring is a pleasure to have! 
    	We believe pronoun is learning a lot.<br />
    	The faculty simple adores pronoun2 and you can often hear 
    	them say \"Attah sex!\"<br />";
    
    //placeholders array
    $placeholders = array('offspring', 'pronoun', 'pronoun2', 'sex');
    //male replace values array
    $malevals = array('son', 'he', 'him', 'boy');
    //female replace values array
    $femalevals = array('daughter', 'she', 'her', 'girl');
    
    //male string
    $malestr = str_replace($placeholders, $malevals, $rawstring);
    
    //female string
    $femalestr = str_replace($placeholders, $femalevals, $rawstring);
    
    echo "Son: ". $malestr . "<br />";
    echo "Daughter: ". $femalestr;
    

    Display:

    Son: Welcome Birmingham parent!
    Your son is a pleasure to have! We believe he is learning a lot.
    The faculty simple adores he2 and you can often hear them say "Attah boy!"

    Daughter: Welcome Birmingham parent!
    Your daughter is a pleasure to have! We believe she is learning a lot.
    The faculty simple adores she2 and you can often hear them say "Attah girl!"

    Notice: there is a bug in this code. The placeholder pronoun2 did not get replaced in the way we intended (our strings have he2 and she2 instead of him and her). This is because all instances of pronoun were replaced first and the pronoun in pronoun2 was replaced at this time with he or she, making he2 or she2. When it was pronoun2's turn to be replaced, there were no matches to be found, so our string has no him or her.

    To fix this bug you could simply make sure that pronoun2 comes first in the placeholders array and by updating the values of the male and female replace values to reflect this.

    PHP Code:

    // ...snip
    //placeholders array
    $placeholders = array('offspring', 'pronoun2', 'pronoun',  'sex');
    //male replace values array
    $malevals = array('son', 'him', 'he',  'boy');
    //female replace values array
    $femalevals = array('daughter', 'her', 'she',  'girl');
    //snip...
    

    Display:

    Son: Welcome Birmingham parent!
    Your son is a pleasure to have! We believe he is learning a lot.
    The faculty simple adores him and you can often hear them say "Attah boy!"

    Daughter: Welcome Birmingham parent!
    Your daughter is a pleasure to have! We believe she is learning a lot.
    The faculty simple adores her and you can often hear them say "Attah girl!"

    substr_replace's Four Parameters

    There are three required parameters for the substr_replace function (original string, replacement string, starting point) and one that's optional (length).

    1. original string - This is your original string that will be operated on.
    2. replacement string - This string will be used to replace everything in the string from the starting point to the ending point (specified by length).
    3. starting point - This is the place in the original string that will be used to mark the replacement's beginning. A negative value specifies the number of characters from the end of the string.
    4. optional length - How many characters from the original string will be replaced. If no length is specified then the end of the string is used. If a value of 0 is used then no characters will be replaced and an insert is performed. A negative value specifies the number of characters from the end of the string.

    substr_replace On Your Mark

    This example of substr_replace shows what happens when you omit the length parameter at various starting points.

    PHP Code:

    //string that needs to be customized
    $original = "ABC123 Hello Mr. Cow! DEF321";
    
    //starting point 5
    $sp5 = substr_replace($original, "Five", 5);
    //starting point 12
    $sp12 = substr_replace($original, "Twelve", 12);
    //starting point 0
    $sp0 = substr_replace($original, "Zero", 0);
    //starting point -1
    $spneg1 = substr_replace($original, "Negative 1", -1);
    
    //Echo each string
    echo "Original String: $original <br />";
    echo "Starting Point 5: $sp5 <br />";
    echo "Starting Point 12: $sp12 <br />";
    echo "Starting Point 0: $sp0 <br />";
    echo "Starting Point -1: $spneg1 ";
    

    Display:

    Original String: ABC123 Hello Mr. Cow! DEF321
    Starting Point 5: ABC12Five
    Starting Point 12: ABC123 HelloTwelve
    Starting Point 0: Zero
    Starting Point -1: ABC123 Hello Mr. Cow! DEF32Negative 1

    As you can see, when you don't specify the fourth parameter, length, everything after the starting point is replaced by the second parameter replacement string.

    Note: The first replacement occurred at position 5, which in $original was the character 3. This 3 and everything onward was replaced with the replacement string. Remember that you start counting character to begin from zero. The $original string could be labeled as so:

    • Letter A - Position 0
    • Letter B - Position 1
    • Letter C - Position 2
    • Letter 1 - Position 3
    • Letter 2 - Position 4
    • Letter 3 - Position 5

    substr_replace Specifying a Length

    If you want to get any sort of precision out of this function you're going to have to get into the nitty gritty of specifying the exact length of characters you want replaced in your original string.

    Imagine that you want to get rid of those ugly pseudo references (ABC123, DEF321) at the beginning and end of the string. Since both of those strings are a length of 6 and we know one is at the very beginning of the string and the other is at the very end of the string we should probably use a starting point of 0 for ABC123 and a value of -6 for DEF321. By having a replacement string of nothing "" we can do something similar to select and delete that we often do in a word processor.

    PHP Code:

    //string that needs to be customized
    $original = "ABC123 Hello Mr. Cow! DEF321";
    
    //remove ABC123 and store in $cleanedstr
    $cleanedstr = substr_replace($original, "", 0, 6);
    //remove DEF321 from $cleanedstr
    $cleanedstr2 = substr_replace($cleanedstr, "", -6, 6);
    
    //Echo each string
    echo "Original String: $original <br />";
    echo "Clean #1: $cleanedstr <br />";
    echo "Clean #2: $cleanedstr2";
    

    Display:

    Original String: ABC123 Hello Mr. Cow! DEF321
    Clean #1: Hello Mr. Cow! DEF321
    Clean #2: Hello Mr. Cow!

    Make sure that you play around with this function some on your own so you can get a feel for how the starting point and length parameters effect this function.

    substr_replace Perform an Insert

    By setting the length parameter to zero you can stop substr_replace from removing anything from the original string and just add to it. If we wanted to add a second and third person to our $original string we would want to do this insert operation. Note: instead of counting the characters we've used a couple other PHP functions to figure out the starting positions for us.

    PHP Code:

    //string that needs to be customized
    $original = "Hello Mr. Cow!";
    
    // Get the position of Mr. Cow
    $cowpos = strpos($original, "Mr. Cow");
    
    // Find where Mr. Cow ends by adding the length of Mr. Cow
    $cowpos_end = $cowpos + strlen("Mr. Cow");
    
    // Insert Mrs. Bear after Mr. Cow
    $mrsbear = substr_replace($original, " and Mrs. Bear", $cowpos_end, 0);
    
    // Insert Sensei Shark before Mr. Cow
    $senseishark = substr_replace($mrsbear, "Sensei Shark, ", $cowpos, 0);
    
    
    //Echo each string
    echo "Original String: $original <br />";
    echo "After Mrs. Bear: $mrsbear <br />";
    echo "After Sensei Shark: $senseishark";
    

    Display:

    Original String: Hello Mr. Cow!
    After Mrs. Bear: Hello Mr. Cow and Mrs. Bear!
    After Sensei Shark: Hello Sensei Shark, Mr. Cow and Mrs. Bear!

    We snuck a new function strlen into that example, but it isn't that complicated of a function, as it stands for "string length."

    • $cowpos_end = $cowpos + strlen("Mr. Cow");

    The strlen function takes a string and then counts up how many characters are in it then returns that number. So by calculating the length of "Mr. Cow" and adding that to the position, we find out where the end point is!



    PHP - String Capitalization Functions

    If you've ever wanted to manipulate the capitalization of your PHP strings, then this lesson will be quite helpful to you. PHP has three primary capitalization related functions: strtoupper, strtolower and ucwords. The function names are pretty self-explanatory, but why they are useful in programming might be new to you.

    Converting a String to Upper Case - strtoupper

    The strtoupper function takes one argument, the string you want converted to upper case and returns the converted string. Only letters of the alphabet are changed, numbers will remain the same.

    PHP Code:

    $originalString = "String Capitalization 1234"; 
    
    $upperCase = strtoupper($originalString);
    echo "Old string - $originalString <br />";
    echo "New String - $upperCase";
    

    Display:

    Old string - String Capitalization 1234
    New String - STRING CAPITALIZATION 1234

    One might use this function to increase emphasis of a important point or in a title. Another time it might be used with a font that looks very nice with all caps to fit the style of the web page design.

    A more technical reason would be to convert two strings you are comparing to see if they are equal. By converting them to the same capitalization you remove the possibility that they won't match simply because of different capitalizations.

    Converting a String to Lower Case - strtolower

    The strtolower function also has one argument: the string that will be converted to lower case.

    PHP Code:

    $originalString = "String Capitalization 1234"; 
    
    $lowerCase = strtolower($originalString);
    echo "Old string - $originalString <br />";
    echo "New String - $lowerCase";
    

    Display:

    Old string - String Capitalization 1234
    New String - string capitalization 1234

    Capitalizing the First Letter - ucwords

    Titles of various media types often capitalize the first letter of each word and PHP has a time-saving function that will do just this.

    PHP Code:

    $titleString = "a title that could use some hELP"; 
    
    $ucTitleString = ucwords($titleString);
    echo "Old title - $titleString <br />";
    echo "New title - $ucTitleString";
    

    Display:

    Old title - a title that could use some hELP
    New title - A Title That Could Use Some HELP

    Notice that the last word "hELP" did not have the capitalization changed on the letters that weren't first, they remained capitalized. If you want to ensure that only the first letter is capitalized in each word of your title, first use the strtolower function and then the ucwords function.

    PHP Code:

    $titleString = "a title that could use some hELP"; 
    
    $lowercaseTitle = strtolower($titleString);
    $ucTitleString = ucwords($lowercaseTitle);
    echo "Old title - $titleString <br />";
    echo "New title - $ucTitleString";
    

    Display:

    Old title - a title that could use some hELP
    New title - A Title That Could Use Some Help


    1. Hello,
    2. I
    3. would
    4. like
    5. to
    6. lose
    7. weight.

    The dynamite (the space character) disappears, but the other stuff remains, but in pieces. With that abstract picture of the explode function in mind, lets take a look at how it really works.

    The explode Function

    The first argument that explode takes is the delimiter (our dynamite) which is used to blow up the second argument, the original string. explode returns an array of string pieces from the original and they are numbered in order, starting from 0. Lets take a phone number in the form ###-###-#### and use a hyphen "-" as our dynamite to split the string into three separate chunks.

    PHP Code:

    $rawPhoneNumber = "800-555-5555"; 
    
    $phoneChunks = explode("-", $rawPhoneNumber);
    echo "Raw Phone Number = $rawPhoneNumber <br />";
    echo "First chunk = $phoneChunks[0]<br />";
    echo "Second chunk = $phoneChunks[1]<br />";
    echo "Third Chunk chunk = $phoneChunks[2]";
    

    Display:

    Raw Phone Number = 800-555-5555
    First chunk = 800
    Second chunk = 555
    Third Chunk chunk = 5555

    explode Function - Setting a Limit

    If you want to control the amount of destruction that explode can wreak on your original string, consider using the third (optional) argument which allows you to set the number of pieces explode can return. This means it will stop exploding once the number of pieces equals the set limit. Below we've blown up a sentence with no limit and then with a limit of 4.

    PHP Code:

    $someWords = "Please don't blow me to pieces."; 
    
    $wordChunks = explode(" ", $someWords);
    for($i = 0; $i < count($wordChunks); $i++){
    	echo "Piece $i = $wordChunks[$i] <br />";
    }
    
    $wordChunksLimited = explode(" ", $someWords, 4);
    for($i = 0; $i < count($wordChunksLimited); $i++){
    	echo "Limited Piece $i = $wordChunksLimited[$i] <br />";
    }
    

    Display:

    Piece 0 = Please
    Piece 1 = don't
    Piece 2 = blow
    Piece 3 = me
    Piece 4 = to
    Piece 5 = pieces.
    Limited Piece 0 = Please
    Limited Piece 1 = don't
    Limited Piece 2 = blow
    Limited Piece 3 = me to pieces.

    The limited explosion has 4 pieces (starting from 0, ending at 3). If you forgot how a for loop works, check out PHP For Loops.



    PHP - Array implode

    The PHP function implode operates on an array and is known as the "undo" function of explode. If you have used explode to break up a string into chunks or just have an array of stuff you can use implode to put them all into one string.

    PHP implode - Repairing the Damage

    The first argument of implode is the string of characters you want to use to join the array pieces together. The second argument is the array (pieces).

    PHP Code:

    $pieces = array("Hello", "World,", "I", "am", "Here!");
    
    $gluedTogetherSpaces = implode(" ", $pieces);
    $gluedTogetherDashes = implode("-", $pieces);
    for($i = 0; $i < count($pieces); $i++){
    	echo "Piece #$i = $pieces[$i] <br />";
    }
    echo "Glued with Spaces = $gluedTogetherSpaces <br />";
    echo "Glued with Dashes = $gluedTogetherDashes";
    

    Display:

    Piece #0 = Hello
    Piece #1 = World,
    Piece #2 = I
    Piece #3 = am
    Piece #4 = Here!
    Glued with Spaces = Hello World, I am Here!
    Glued with Dashes = Hello-World,-I-am-Here!

    The implode function will convert the entire array into a string and there is no optional argument to limit this as there was in the explode function.

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  • PHP Date, Session, Cookies ↓

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    PHP Date Function

    While PHP's date() function may seem to have an overwhelming amount of options available, isn't it always better to have more choices than not enough? With PHP's date function you format timestamps, so they are more human readable.

    This lesson will teach you how to display the current time, formating PHP's timestamp, and show you all the various date arguments for reference purposes.

    PHP Date - The Timestamp

    The date function always formats a timestamp, whether you supply one or not. What's a timestamp? Good question!

    • Timestamp: A timestamp is the number of seconds from January 1, 1970 at 00:00. Otherwise known as the Unix Timestamp, this measurement is a widely used standard that PHP has chosen to utilize.

    What Time Is It?

    The date function uses letters of the alphabet to represent various parts of a typical date and time format. The letters we will be using in our first example are:

    • d: The day of the month. The type of output you can expect is 01 through 31.
    • m: The current month, as a number. You can expect 01 through 12.
    • y: The current year in two digits ##. You can expect 00 through 99

    We'll tell you the rest of the options later, but for now let's use those above letters to format a simple date! The letters that PHP uses to represent parts of date and time will automatically be converted by PHP.

    However, other characters like a slash "/" can be inserted between the letters to add additional formatting. We have opted to use the slash in our example.

    PHP Code:

    <?php
    echo date("m/d/y"); 
    ?>
    

    If the 2010 Winter Olympics were just finishing up, you would see something like:

    Display:

    02/27/10

    Be sure to test this out on your own PHP enabled server, it's really great to see the instant results available with PHP date!

    Supplying a Timestamp

    As our first example shows, the first argument of the date function tells PHP how you would like your date and time displayed. The second argument allows for a timestamp and is optional.

    This example uses the mktime function to create a timestamp for tomorrow. To go one day in the future we simply add one to the day argument of mktime. For your future reference, we have the arguments of mktime.

    Note: These arguments are all optional. If you do not supply any arguments the current time will be used to create the timestamp.

    • mktime(hour, minute, second, month, day, year, daylight savings time)

    PHP Code:

    <?php
    $tomorrow = mktime(0, 0, 0, date("m"), date("d")+1, date("y"));
    echo "Tomorrow is ".date("m/d/y", $tomorrow); 
    ?>
    

    Notice that we used one letter at a time with the function date to get the month, day and year. For example the date("m") will return the month's number 01-12.

    If we were to run our new script just after the 2010 Winter Olympics our display would look like:

    Display:

    Tomorrow is 02/28/10

    PHP Date - Reference

    Now that you know the basics of using PHP's date function, you can easily plug in any of the following letters to format your timestamp to meet your needs.

    Important Full Date and Time:
    • r: Displays the full date, time and timezone offset. It is equivalent to manually entering date("D, d M Y H:i:s O")
    Time:
    • a: am or pm depending on the time
    • A: AM or PM depending on the time
    • g: Hour without leading zeroes. Values are 1 through 12.
    • G: Hour in 24-hour format without leading zeroes. Values are 0 through 23.
    • h: Hour with leading zeroes. Values 01 through 12.
    • H: Hour in 24-hour format with leading zeroes. Values 00 through 23.
    • i: Minute with leading zeroes. Values 00 through 59.
    • s: Seconds with leading zeroes. Values 00 through 59.
    Day:
    • d: Day of the month with leading zeroes. Values are 01 through 31.
    • j: Day of the month without leading zeroes. Values 1 through 31
    • D: Day of the week abbreviations. Sun through Sat
    • l: Day of the week. Values Sunday through Saturday
    • w: Day of the week without leading zeroes. Values 0 through 6.
    • z: Day of the year without leading zeroes. Values 0 through 365.
    Month:
    • m: Month number with leading zeroes. Values 01 through 12
    • n: Month number without leading zeroes. Values 1 through 12
    • M: Abbreviation for the month. Values Jan through Dec
    • F: Normal month representation. Values January through December.
    • t: The number of days in the month. Values 28 through 31.
    Year:
    • L: 1 if it's a leap year and 0 if it isn't.
    • Y: A four digit year format
    • y: A two digit year format. Values 00 through 99.
    Other Formatting:
    • U: The number of seconds since the Unix Epoch (January 1, 1970)
    • O: This represents the Timezone offset, which is the difference from Greenwich Meridian Time (GMT). 100 = 1 hour, -600 = -6 hours

    We suggest that you take a few minutes to create several timestamps using PHP's mktime function and just try out all these different letters to get your feet wet with PHP's date function.




    PHP Sessions - Why Use Them?

    As a website becomes more sophisticated, so must the code that backs it. When you get to a stage where your website need to pass along user data from one page to another, it might be time to start thinking about using PHP sessions.

    A normal HTML website will not pass data from one page to another. In other words, all information is forgotten when a new page is loaded. This makes it quite a problem for tasks like a shopping cart, which requires data(the user's selected product) to be remembered from one page to the next.

    PHP Sessions - Overview

    A PHP session solves this problem by allowing you to store user information on the server for later use (i.e. username, shopping cart items, etc). However, this session information is temporary and is usually deleted very quickly after the user has left the website that uses sessions.

    It is important to ponder if the sessions' temporary storage is applicable to your website. If you require a more permanent storage you will need to find another solution, like a MySQL database.

    Sessions work by creating a unique identification(UID) number for each visitor and storing variables based on this ID. This helps to prevent two users' data from getting confused with one another when visiting the same webpage.

    Note:If you are not experienced with session programming it is not recommended that you use sessions on a website that requires high-security, as there are security holes that take some advanced techniques to plug.

    Starting a PHP Session

    Before you can begin storing user information in your PHP session, you must first start the session. When you start a session, it must be at the very beginning of your code, before any HTML or text is sent.

    Below is a simple script that you should place at the beginning of your PHP code to start up a PHP session.

    PHP Code:

    <?php
    session_start(); // start up your PHP session! 
    ?>
    

    This tiny piece of code will register the user's session with the server, allow you to start saving user information and assign a UID (unique identification number) for that user's session.

    Storing a Session Variable

    When you want to store user data in a session use the $_SESSION associative array. This is where you both store and retrieve session data. In previous versions of PHP there were other ways to perform this store operation, but it has been updated and this is the correct way to do it.

    PHP Code:

    <?php
    session_start(); 
    $_SESSION['views'] = 1; // store session data
    echo "Pageviews = ". $_SESSION['views']; //retrieve data
    ?>
    

    Display:

    Pageviews = 1

    In this example we learned how to store a variable to the session associative array $_SESSION and also how to retrieve data from that same array.

    PHP Sessions: Using PHP's isset Function

    Now that you are able to store and retrieve data from the $_SESSION array, we can explore some of the real functionality of sessions. When you create a variable and store it in a session, you probably want to use it in the future. However, before you use a session variable it is necessary that you check to see if it exists already!

    This is where PHP's isset function comes in handy. isset is a function that takes any variable you want to use and checks to see if it has been set. That is, it has already been assigned a value.

    With our previous example, we can create a very simple pageview counter by using isset to check if the pageview variable has already been created. If it has we can increment our counter. If it doesn't exist we can create a pageview counter and set it to one. Here is the code to get this job done:

    PHP Code:

    <?php
    session_start();  
    if(isset($_SESSION['views']))
        $_SESSION['views'] = $_SESSION['views']+ 1;
    else
        $_SESSION['views'] = 1;
    
    echo "views = ". $_SESSION['views']; 
    ?>
    

    The first time you run this script on a freshly opened browser the if statement will fail because no session variable views would have been stored yet. However, if you were to refresh the page the if statement would be true and the counter would increment by one. Each time you reran this script you would see an increase in view by one.

    Cleaning and Destroying your Session

    Although a session's data is temporary and does not require that you explicitly clean after yourself, you may wish to delete some data for your various tasks.

    Imagine that you were running an online business and a user used your website to buy your goods. The user has just completed a transaction on your website and you now want to remove everything from their shopping cart.

    PHP Code:

    <?php
    session_start();  
    if(isset($_SESSION['cart']))
        unset($_SESSION['cart']); 
    ?>
    

    You can also completely destroy the session entirely by calling the session_destroy function.

    PHP Code:

    <?php
    session_start(); 
    session_destroy();
    ?>
    

    Destroy will reset your session, so don't call that function unless you are entirely comfortable losing all your stored session data!




    PHP Cookies - Background

    Cookies have been around for quite some time on the internet. They were invented to allow webmaster's to store information about the user and their visit on the user's computer.

    At first they were feared by the general public because it was believed they were a serious privacy risk. Nowadays nearly everyone has cookies enabled on their browser, partly because there are worse things to worry about and partly because all of the "trustworthy" websites now use cookies.

    This lesson will teach you the basics of storing a cookie and retrieving a cookie, as well as explaining the various options you can set with your cookie.

    Creating Your First PHP Cookie

    When you create a cookie, using the function setcookie, you must specify three arguments. These arguments are setcookie(name, value, expiration):

    1. name: The name of your cookie. You will use this name to later retrieve your cookie, so don't forget it!
    2. value: The value that is stored in your cookie. Common values are username(string) and last visit(date).
    3. expiration: The date when the cookie will expire and be deleted. If you do not set this expiration date, then it will be treated as a session cookie and be removed when the browser is restarted.

    In this example we will be creating a cookie that stores the user's last visit to measure how often people return to visit our webpage. We want to ignore people that take longer than two months to return to the site, so we will set the cookie's expiration date to two months in the future!

    PHP Code:

    <?php
    //Calculate 60 days in the future
    //seconds * minutes * hours * days + current time
    $inTwoMonths = 60 * 60 * 24 * 60 + time(); 
    setcookie('lastVisit', date("G:i - m/d/y"), $inTwoMonths); 
    ?>
    

    Don't worry if you can't follow the somewhat involved date calculations in this example. The important part is that you know how to set a cookie, by specifying the three important arguments: name, value and expiration date.

    Retrieving Your Fresh Cookie

    If your cookie hasn't expired yet, let's retrieve it from the user's PC using the aptly named $_COOKIE associative array. The name of your stored cookie is the key and will let you retrieve your stored cookie value!

    PHP Code:

    <?php
    if(isset($_COOKIE['lastVisit']))
    	$visit = $_COOKIE['lastVisit']; 
    else
    	echo "You've got some stale cookies!";
    
    echo "Your last visit was - ". $visit;
    ?>
    

    This handy script first uses the isset function to be sure that our "lastVisit" cookie still exists on the user's PC, if it does, then the user's last visit is displayed. If the user visited our site on February 28, 2008 it might look something like this:

    Display:

    Your last visit was - 11:48 - 02/28/08
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  • PHP CLASSES ↓

    Introduction to PHP classes

    While classes and the entire concept of Object Oriented Programming (OOP) is the basis of lots of modern programming languages, PHP was built on the principles of functions instead. Basic support for classes was first introduced in version 4 of PHP but then re-written for version 5, for a more complete OOP support. Today, PHP is definitely usable for working with classes, and while the PHP library still mainly consists of functions, classes are now being added for various purposes. However, the main purpose is of course to write and use your own classes, which is what we will look into during the next chapters.

    Classes can be considered as a collection of methods, variables and constants. They often reflect a real-world thing, like a Car class or a Fruit class. You declare a class only once, but you can instantiate as many versions of it as can be contained in memory. An instance of a class is usually referred to as an object.

    If you're still a bit confused about what classes are and why you need them, don't worry. In the next chapter, we will write our very first class and use it. Hopefully that will give you a better idea of the entire concept.


    Defining and using a class

    After the introduction to classes in the previous chapter, we're now ready to write our very own class. It will hold information about a generic user, for instance a user of your website.

    A class definition in PHP looks pretty much like a function declaration, but instead of using the function keyword, the class keyword is used. Let's start with a stub for our User class:
    <?php
    class User
    {
        
    }
    ?>
    
    This is as simple as it gets, and as you can probably imagine, this class can do absolutely nothing at this point. We can still instantiate it though, which is done using the new keyword:

    $user = new User();

    But since the class can't do anything yet, the $user object is just as useless. Let's remedy that by adding a couple of class variables and a method:
    class User
    {
        public $name;
        public $age;
        
        public function Describe()
        {
            return $this->name . " is " . $this->age . " years old";
        }
    }
    
    Okay, there are a couple of new concepts here. First of all, we declare two class variables, a name and an age. The variable name is prefixed by the access modifier "public", which basically means that the variable can be accessed from outside the class. We will have much more about access modifiers in one of the next chapters.

    Next, we define the Describe() function. As you can see, it looks just like a regular function declaration, but with a couple of exceptions. It has the public keyword in front of it, to specify the access modifier. Inside the function, we use the "$this" variable, to access the variables of the class it self. $this is a special variable in PHP, which is available within class functions and always refers to the object from which it is used.

    Now, let's try using our new class. The following code should go after the class has been declared or included:
    $user = new User();
    $user->name = "John Doe";
    $user->age = 42;
    echo $user->Describe();
    
    The first thing you should notice is the use of the -> operator. We used it in the Describe() method as well, and it simply denotes that we wish to access something from the object used before the operator. $user->name is the same as saying "Give me the name variable on the $user object". After that, it's just like assigning a value to a normal variable, which we do twice, for the name and the age of the user object. In the last line, we call the Describe() method on the user object, which will return a string of information, which we then echo out. The result should look something like this:

    John Doe is 42 years old

    Congratulations, you have just defined and used your first class, but there is much more to classes than this. In the following chapters, we will have a look at all the possibilities of PHP classes.


    Constructors and destructors

    A constructor and a destructor are special functions which are automatically called when an object is created and destroyed. The constructor is the most useful of the two, especially because it allows you to send parameters along when creating a new object, which can then be used to initialize variables on the object. Here's an example of a class with a simple constructor:
    class Animal
    {
        public $name = "No-name animal";
        
        public function __construct()
        {
            echo "I'm alive!";        
        }
    }
    
    As you can see, the constructor looks just like a regular function, except for the fact that it starts with two underscores. In PHP, functions with two underscore characters before the name usually tells you that it's a so-called magic function, a function with a specific purpose and extra functionality, in comparison to normal functions. So, a function with the exact name "__construct", is the constructor function of the class and will be called automatically when the object is created. Let's try doing just that:

    $animal = new Animal();

    With just that line of code, the object will be created, the constructor called and the lines of code in it executed, which will cause our "I'm alive!" line to be outputted. However, as mentioned previously, a big advantage of the constructor is the ability to pass parameters which can be used to initialize member variables. Let's try doing just that:
    <?php
    class Animal
    {
        public $name = "No-name animal";
        
        public function __construct($name)
        {
            $this->name = $name;
        }
    }
    
    $animal = new Animal("Bob the Dog");
    echo $animal->name;
    ?>
    
    Declaring the constructor with parameters is just like declaring a regular function, and passing the parameter(s) is much like calling a regular function, but of course with the "new" keyword that we introduced earlier. A constructor can have as many parameters as you want.

    Destructors

    A destructor is called when the object is destroyed. In some programming languages, you have to manually dispose of objects you created, but in PHP, it's handled by the Garbage Collector, which keeps an eye on your objects and automatically destroys them when they are no longer needed. Have a look at the following example, which is an extended version of our previous example:
    <?php
    class Animal
    {
        public $name = "No-name animal";
        
        public function __construct($name)
        {
            echo "I'm alive!";    
            $this->name = $name;
        }
        
        public function __destruct()
        {
            echo "I'm dead now :(";
        }
    }
    
    $animal = new Animal("Bob");
    echo "Name of the animal: " . $animal->name;
    ?>
    
    As you can see, the destructor is just like a constructor, only the name differs. If you try running this example, you will see first the constructor message, then the name of the animal that we manually output in the last line, and after that, the script ends, the object is destroyed, the destructor is called and the message about our poor animal being dead is outputted.


    Visibility

    Visibility is a big part of OOP. It allows you to control where your class members can be accessed from, for instance to prevent a certain variable to be modified from outside the class. The default visibility is public, which means that the class members can be accessed from anywhere. This means that declaring the visibility is optional, since it will just fall back to public if there is no access modifier. For backwards compatibility, the old way of declaring a class variable, where you would prefix the variable name with the "var" keyword (this is from PHP 4 and should not be used anymore) will also default to public visibility.

    PHP is pretty simple in this area, because it comes with only 3 different access modifiers: private, protected and public.

    Private members can only be accessed from inside the class itself.

    Protected members can only be accessed from inside the class it self and its child classes.

    Public members can be accessed from anywhere - outside the class, inside the class it self and from child classes.


    Inheritance

    Inheritance is one of the most important aspects of OOP. It allows a class to inherit members from another class. Understanding why this is smart without an example can be pretty difficult, so let's start with one of those.

    Imagine that you need to represent various types of animals. You could create a Cat class, a Dog class and so on, but you would probably soon realize that these classes would share quite a bit of functionality. On the other hand, there could be stuff that would have to be specific for each animal. For a case like this, inheritance is really great. The idea is to create a base class, in this case called Animal, and then create a child class for each specific animal you need. Another advantage to this approach is that you will every animal you have will come with the same basic functionality that you can always rely on.

    Again, this can seem very theoretic and you might not find it very useful in the beginning, but as you create more advanced websites, you will likely run into situations where inheritance can come in handy. Let's have a look at an example now:
    class Animal
    {
        public $name;
        
        public function Greet()
        {
            return "Hello, I'm some sort of animal and my name is " . $this->name;
        }
    }
    
    A very simple class, pretty much like the ones we created in a previous chapter. However, "some sort of animal" is not very descriptive, so let's create a child class for a dog:
    class Dog extends Animal
    {
        
    }
    
    The dog is declared like a regular class, but after that, we use the extends keyword to tell PHP that the Dog class should inherit from the Animal class. Right now, our Dog class has the exact same functionality as the Animal class. Verify this by running the following code:
    $dog = new Dog();
    echo $dog->Greet();
    
    You will see that both the name and the Greet() function is still there, but they are also still very anonymous. Let's change that by writing a specific version of the Greet() function for our Dog:
    class Dog extends Animal
    {
        public function Greet()
        {
            return "Hello, I'm a dog and my name is " . $this->name;
        }
    }
    
    Notice that we declare the Greet() function again, because we need for it to do something else, but the $name class variable is not declared - we already have that defined on the Animal class, which is just fine. As you can see, even though $name is not declared on the Dog class, we can still use it in its Greet() function. Now, with both classes declared, it's time to test them out. The following code will do that for us:
    $animal = new Animal();
    echo $animal->Greet();
    $animal = new Dog();
    $animal->name = "Bob";
    echo $animal->Greet();
    
    We start out by creating an instance of an Animal class and then call the Greet() function. The result should be the generic greeting we wrote first. After that, we assign a new instance of the Dog class to the $animal variable, assign a real name to our dog and then call the Greet() function again. This time, the Dog specific Greet() function is used and we get a more specific greeting from our animal, because it's now a dog.

    Inheritance works recursively as well - you can create a class that inherits from the Dog class, which in turn inherits from the Animal class, for instance a Puppy class. The Puppy class will then have variables and methods from both the Dog and the Animal class.


    Abstract classes

    Abstract classes are special because they can never be instantiated. Instead, you typically inherit a set of base functionality from them in a new class. For that reason, they are commonly used as the base classes in a larger class hierarchy. In the chapter on inheritance, we created an Animal class and then a Dog class to inherit from the Animal class. In your project, you may very well decide that no one should be able to instantiate the Animal class, because it's too unspecific, but instead use a specific class inheriting from it. The Animal class will then serve as a base class for our own little collection of animals.

    A method can be marked as abstract as well. As soon as you mark a class function as abstract, you have to define the class as abstract as well - only abstract classes can hold abstract functions. Another consequence is that you don't have to (and can't) write any code for the function - it's a declaration only. You would do this to force anyone inheriting from your abstract class to implement this function and write the proper code for it. If you don't, PHP will throw an error. However, abstract classes can also contain non-abstract methods, which allows you to implement basic functionality in the abstract class. Let's go on with an example. Here is the abstract class:
    abstract class Animal
    {
        public $name;
        public $age;
        
        public function Describe()
        {
            return $this->name . ", " . $this->age . " years old";    
        }
        
        abstract public function Greet();
    }
    
    As you can see, it looks like a regular exception, but with a couple of differences. The first one is the abstract keyword, which is used to mark both the class it self and the last function as abstract. As mentioned, an abstract function can't contain any body (code), so it's simply ended with a semi-colon as you can see. Now let's create a class that can inherit our Animal class:
    class Dog extends Animal
    {
        public function Greet()
        {
            return "Woof!";    
        }
        
        public function Describe()
        {
            return parent::Describe() . ", and I'm a dog!";    
        }
    }
    
    As you can see, we implement the both functions from the Animal class. The Greet() function we are forced to implement, since it's marked as abstract - it simply returns a word/sound common to the type of animal we are creating. We are not forced to implement the Describe() function - it's already implemented on the Animal class, but we would like to extend the functionality of it a bit. Now, the cool part is that we can re-use the code implemented in the Animal class, and then add to it as we please. In this case, we use the parent keyword to reference the Animal class, and then we call Describe() function on it. We then add some extra text to the result, to clarify which type of animal we're dealing with. Now, let's try using this new class:
    $animal = new Dog();
    $animal->name = "Bob";
    $animal->age = 7;
    echo $animal->Describe();
    echo $animal->Greet();
    
    Nothing fancy here, really. We just instantiate the Dog class, set the two properties and then call the two methods defined on it. If you test this code, you will see that the Describe() method is now a combination of the Animal and the Dog version, as expected.


    Static classes

    Since a class can be instantiated more than once, it means that the values it holds, are unique to the instance/object and not the class itself. This also means that you can't use methods or variables on a class without instantiating it first, but there is an exception to this rule. Both variables and methods on a class can be declared as static (also referred to as "shared" in some programming languages), which means that they can be used without instantiating the class first. Since this means that a class variable can be accessed without a specific instance, it also means that there will only be one version of this variable. Another consequence is that a static method cannot access non-static variables and methods, since these require an instance of the class.

    In a previous chapter, we wrote a User class. Let's expand it with some static functionality, to see what the fuzz is all about:
    <?php
    class User
    {
        public $name;
        public $age;
        public static $minimumPasswordLength = 6;
        
        public function Describe()
        {
            return $this->name . " is " . $this->age . " years old";
        }
        
        public static function ValidatePassword($password)
        {
            if(strlen($password) >= self::$minimumPasswordLength)
                return true;
            else
                return false;
        }
    }
    
    $password = "test";
    if(User::ValidatePassword($password))
        echo "Password is valid!";
    else
        echo "Password is NOT valid!";
    ?>
    
    What we have done to the class, is adding a single static variable, the $minimumPasswordLength which we set to 6, and then we have added a static function to validate whether a given password is valid. I admit that the validation being performed here is very limited, but obviously it can be expanded. Now, couldn't we just do this as a regular variable and function on the class? Sure we could, but it simply makes more sense to do this statically, since we don't use information specific to one user - the functionality is general, so there's no need to have to instantiate the class to use it.

    As you can see, to access our static variable from our static method, we prefix it with the self keyword, which is like this but for accessing static members and constants. Obviously it only works inside the class, so to call the ValidatePassword() function from outside the class, we use the name of the class. You will also notice that accessing static members require the double-colon operator instead of the -> operator, but other than that, it's basically the same.

    Class constants

    A constant is, just like the name implies, a variable that can never be changed. When you declare a constant, you assign a value to it, and after that, the value will never change. Normally, simple variables are just easier to use, but in certain cases constants are preferable, for instance to signal to other programmers (or your self, in case you forget) that this specific value should not be changed during runtime.

    Class constants are just like regular constants, except for the fact that they are declared on a class and therefore also accessed through this specific class. Just like with static members, you use the double-colon operator to access a class constant. Here is a basic example:
    <?php
    class User
    {
        const DefaultUsername = "John Doe";
        const MinimumPasswordLength = 6;
    }
    
    echo "The default username is " . User::DefaultUsername;
    echo "The minimum password length is " . User::MinimumPasswordLength;
    ?>
    
    As you can see, it's much like declaring variables, except there is no access modifier - a constant is always publically available. As required, we immediately assign a value to the constants, which will then stay the same all through execution of the script. To use the constant, we write the name of the class, followed by the double-colon operator and then the name of the constant. That's really all there is to it.


    The "final" keyword

    In the previous chapters, we saw how we could let a class inherit from another class. We also saw how you could override a function in an inherited class, to replace the behaviour originally provided. However, in some cases you may want to prevent a class from being inherited from or a function to be overridden. This can be done with the final keyword, which simply causes PHP to throw an error if anyone tries to extend your final class or override your final function.

    A final class could look like this:
    final class Animal
    {
        public $name;
    }
    
    
    A class with a final function could look like this:
    class Animal
    {
        final public function Greet()
        {
            return "The final word!";    
        }
    }
    
    The two can be combined if you need to, but they can also be used independently, as seen in the examples above.
  • PHP SENDING EMAILS↓

    PHP must be configured correctly in the php.ini file with the details of how your system sends email. Open php.ini file available in /etc/ directory and find the section headed [mail function].

    Windows users should ensure that two directives are supplied. The first is called SMTP that defines your email server address. The second is called sendmail_from which defines your own email address.

    The configuration for Windows should look something like this −

    [mail function]
    ; For Win32 only.
    SMTP = smtp.secureserver.net
    
    ; For win32 only
    sendmail_from = webmaster@tutorialspoint.com
    

    Linux users simply need to let PHP know the location of their sendmail application. The path and any desired switches should be specified to the sendmail_path directive.

    The configuration for Linux should look something like this −

    [mail function]
    ; For Win32 only.
    SMTP = 
    
    ; For win32 only
    sendmail_from = 
    
    ; For Unix only
    sendmail_path = /usr/sbin/sendmail -t -i
    

    Now you are ready to go −

    Sending plain text email

    PHP makes use of mail() function to send an email. This function requires three mandatory arguments that specify the recipient's email address, the subject of the the message and the actual message additionally there are other two optional parameters.

    mail( to, subject, message, headers, parameters );
    

    Here is the description for each parameters.

    Parameter Description
    to Required. Specifies the receiver / receivers of the email
    subject Required. Specifies the subject of the email. This parameter cannot contain any newline characters
    message Required. Defines the message to be sent. Each line should be separated with a LF (\n). Lines should not exceed 70 characters
    headers Optional. Specifies additional headers, like From, Cc, and Bcc. The additional headers should be separated with a CRLF (\r\n)
    parameters Optional. Specifies an additional parameter to the send mail program

    As soon as the mail function is called PHP will attempt to send the email then it will return true if successful or false if it is failed.

    Multiple recipients can be specified as the first argument to the mail() function in a comma separated list.

    Sending HTML email

    When you send a text message using PHP then all the content will be treated as simple text. Even if you will include HTML tags in a text message, it will be displayed as simple text and HTML tags will not be formatted according to HTML syntax. But PHP provides option to send an HTML message as actual HTML message.

    While sending an email message you can specify a Mime version, content type and character set to send an HTML email.

    Example

    Following example will send an HTML email message to xyz@somedomain.com copying it to afgh@somedomain.com. You can code this program in such a way that it should receive all content from the user and then it should send an email.

    <html>
       
       <head>
          <title>Sending HTML email using PHP</title>
       </head>
       
       <body>
          
          <?php
             $to = "xyz@somedomain.com";
             $subject = "This is subject";
             
             $message = "<b>This is HTML message.</b>";
             $message .= "<h1>This is headline.</h1>";
             
             $header = "From:abc@somedomain.com \r\n";
             $header = "Cc:afgh@somedomain.com \r\n";
             $header .= "MIME-Version: 1.0\r\n";
             $header .= "Content-type: text/html\r\n";
             
             $retval = mail ($to,$subject,$message,$header);
             
             if( $retval == true )
             {
                echo "Message sent successfully...";
             }
             else
             {
                echo "Message could not be sent...";
             }
          ?>
          
       </body>
    </html>
    

    Sending attachments with email

    To send an email with mixed content requires to set Content-type header to multipart/mixed. Then text and attachment sections can be specified within boundaries.

    A boundary is started with two hyphens followed by a unique number which can not appear in the message part of the email. A PHP function md5() is used to create a 32 digit hexadecimal number to create unique number. A final boundary denoting the email's final section must also end with two hyphens.

    <?php
       // request variables // important
       $from=$_REQUEST["from"];
       $emaila=$_REQUEST["emaila"];
       $filea=$_REQUEST["filea"];
       
       if ($filea)
       {
          function mail_attachment ($from , $to, $subject, $message, $attachment){
             $fileatt = $attachment; // Path to the file
             $fileatt_type = "application/octet-stream"; // File Type 
             
             $start = strrpos($attachment, '/') == -1 ? strrpos($attachment, '//') : strrpos($attachment, '/')+1;
             $fileatt_name = substr($attachment, $start, strlen($attachment)); // Filename that will be used for the file as the attachment 
             
             $email_from = $from; // Who the email is from
             $subject = "New Attachment Message";
             
             $email_subject =  $subject; // The Subject of the email 
             $email_txt = $message; // Message that the email has in it 
             $email_to = $to; // Who the email is to
             
             $headers = "From: ".$email_from;
             $file = fopen($fileatt,'rb'); 
             $data = fread($file,filesize($fileatt)); 
             fclose($file); 
             
             $msg_txt="\n\n You have recieved a new attachment message from $from";
             $semi_rand = md5(time()); 
             $mime_boundary = "==Multipart_Boundary_x{$semi_rand}x"; 
             $headers .= "\nMIME-Version: 1.0\n" . "Content-Type: multipart/mixed;\n" . " boundary=\"{$mime_boundary}\"";
             
             $email_txt .= $msg_txt;
             $email_message .= "This is a multi-part message in MIME format.\n\n" . "--{$mime_boundary}\n" . "Content-Type:text/html; charset=\"iso-8859-1\"\n" . "Content-Transfer-Encoding: 7bit\n\n" . $email_txt . "\n\n";
             $data = chunk_split(base64_encode($data));
             
             $email_message .= "--{$mime_boundary}\n" . "Content-Type: {$fileatt_type};\n" . " name=\"{$fileatt_name}\"\n" . //"Content-Disposition: attachment;\n" . //" filename=\"{$fileatt_name}\"\n" . "Content-Transfer-Encoding: base64\n\n" . $data . "\n\n" . "--{$mime_boundary}--\n";
             $ok = mail($email_to, $email_subject, $email_message, $headers);
             
             if($ok)
             {
                echo "File Sent Successfully.";
                unlink($attachment); // delete a file after attachment sent.
             }
             
             else
             {
                die("Sorry but the email could not be sent. Please go back and try again!");
             }
          }
          move_uploaded_file($_FILES["filea"]["tmp_name"],'temp/'.basename($_FILES['filea']['name']));
          mail_attachment("$from", "youremailaddress@gmail.com", "subject", "message", ("temp/".$_FILES["filea"]["name"]));
       }
    ?>
    
    <html>
       <head>
          
          <script language="javascript" type="text/javascript">
             function CheckData45()
             {
                with(document.filepost)
                {
                   if(filea.value != "")
                   {
                      document.getElementById('one').innerText = "Attaching File ... Please Wait";
                   }
                }
             }
          </script>
          
       </head>
       <body>
          
          <table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
             <tr>
                <td align="center">
                   <form name="filepost" method="post" action="file.php" enctype="multipart/form-data" id="file">
                      
                      <table width="300" border="0" cellspacing="0" cellpadding="0">
                         <tr valign="bottom">
                            <td height="20">Your Name:</td>
                         </tr>
                         
                         <tr>
                            <td><input name="from" type="text" id="from" size="30"></td>
                         </tr>
                         
                         <tr valign="bottom">
                            <td height="20">Your Email Address:</td>
                         </tr>
                         
                         <tr>
                            <td class="frmtxt2"><input name="emaila" type="text" id="emaila" size="30"> </td>
                         </tr>
                         
                         <tr>
                            <td height="20" valign="bottom">Attach File:</td>
                         </tr>
                         
                         <tr valign="bottom">
                            <td valign="bottom"><input name="filea" type="file" id="filea" size="16"></td>
                         </tr>
                         
                         <tr>
                            <td height="40" valign="middle"><input name="Reset2" type="reset" id="Reset2" value="Reset">
                            <input name="Submit2" type="submit" value="Submit" onClick="return CheckData45()"></td>
                         </tr>
                      </table>
                      
                   </form>
                   
                   <center>
                      <table width="400">
                         <tr>
                            <td id="one">
                            </td>
                         </tr>
                      </table>
                   </center>
                   
                </td>
             </tr>
          </table>
          
       </body>
    </html>
    
  • MYSQL WITH PHP ↓

    A database is your best choice for storing data in your web application, and the MySQL database server has always been the most popular choice among PHP developers. It's supported by almost any hosting company offering PHP, which makes it easy to get started with, and you can even download and install it on your own computer, for testing purposes.

    MySQL uses the SQL (Structured Query Language) programming language to work with the data, and PHP interacts with MySQL by simply passing SQL code through a set of MySQL functions to the MySQL server, which then returns a result that PHP can interpret. It can seem a bit scary to have to learn a second language to interact with databases, but fortunately SQL is a fairly simple language, which looks a lot like the English language and we will provide you with some good SQL examples, allowing you to do the most common tasks.

    In the following chapters we will work with the MySQL database and make it do various things for us. To do it properly, we need some common test data, which you will need to add to a database for which you have access to. The easiest way to do this is to use one of the many MySQL tools, with the most popular one being phpMyAdmin, which is installed on most servers offering PHP and MySQL. If you don't have access to phpMyAdmin, you can install it, use one of the many downloadable applications or use the MySQL prompt. Whatever you choose, you should execute the following SQL code against your database. In phpMyAdmin, this is done by clicking the button labelled "SQL":
    CREATE TABLE `test_users` (
      `id` int(11) NOT NULL auto_increment,
      `name` varchar(100) NOT NULL default '',
      `country` varchar(100) NOT NULL default '',
      PRIMARY KEY  (`id`)
    ); 
    
    INSERT INTO `test_users` VALUES (1,'David','USA');
    INSERT INTO `test_users` VALUES (2,'Sammy','Canada');
    INSERT INTO `test_users` VALUES (3,'Heidi','Germany');
    INSERT INTO `test_users` VALUES (4,'Pierre','France');
    INSERT INTO `test_users` VALUES (5,'Carlos','Spain');
    
    When your done, a new table called "test_users" should have been created and filled with a small amount of testing data. In the next chapters we will work with it. If you're working with your own installation of PHP, please make sure that MySQL support has been enabled. This can be done in the php.ini file.


    Establishing a connection

    In the previous chapter, we created a database table with some test data. Now we need to establish a connection to the database server so that we can start working with the data. Connecting to a MySQL database with PHP is very easy. It can be done using a single function from the nice array of MySQL related functions in PHP:

    mysql_connect("localhost", "username", "password");

    If default values have been configured in your configuration file, you can leave out these parameters, but otherwise you will need to specify a host and typically a username and a password for it. Both the username and password has been set by yourself or by your hosting company. If you host MySQL on your own machine, or if you run your PHP code on your hosting company's server, you can usually just specify localhost as the host value. If in doubt, ask your hosting company or check their support pages.

    The mysql_connect() function returns a resource, a direct link to the database server, which should be used to access the database server each time you use one of the MySQL functions. However, if this resource is not specified, PHP will just use the last opened connection, allowing you to write less code. In most cases you will only need one MySQL connection per page, so this should work just fine for you.

    To work with a database, you need to call one more function, the mysql_select_db() function. The name really tells it all - for a specific connection, it selects a database that you will be working with. It's very simple to use:

    mysql_select_db("my_database");

    This should be called after you have established the connection using mysql_connect(). It takes one or two parameters. The first should be the name of the database you wish to use. The second one is optional and allows you to specify which MySQL resource link the function should be performed on. Here is an example where we use these two essential functions together:
    mysql_connect("localhost", "username", "password");
    mysql_select_db("my_database");
    
    And here is the same example, but where we get the resource link from mysql_connect() and use it. This is the way you should do it mainly if you need to connect to more than one database server on the same page:
    $dbConnection = mysql_connect("localhost", "username", "password");
    mysql_select_db("my_database", $dbConnection);
    
    With this, we now have a connection to the database server and we have selected the desired database. In the next chapter, we will use this connection, but before we do so, we should talk a bit about closing the connection again. A connection to a database server is costly, so it should obviously be closed once we're done using it. However, PHP can and will do this for us automatically, if we choose not to do it, once the page is fully executed. If we for some reason want to close a MySQL connection before the page is done executing, we can do it by using the mysql_close() function:

    mysql_close();

    This will close the last opened connection. If we want to close a specific connection, just pass its link to the function:

    mysql_close($dbConnection);

    Okay, with a good understanding of how a connection is started, we can now move on to using it. Read on.


    Retrieving data

    In the last chapter, we established a connection to your MySQL database, so by now its time to do something interestingly with the connection. As mentioned in the introduction, we interact with the MySQL server by sending SQL code through a PHP function, more specifically the mysql_query() function.

    To retrieve data through SQL, the SELECT statement is used. It comes in many variations, but it its most simple form, it typically looks like this:

    SELECT column_name FROM table_name

    This query will select data from the column called "column_name" in the table called "table_name" and return all rows of it. In the introduction chapter, we inserted some rows of data in our test_users table, where we have the columns id, name and country. To get this data, our query could look like this:

    SELECT id, name, country FROM test_users

    That's the SQL needed to retrieve our data. Let's make PHP execute it for us, by using the mysql_query() function:
    mysql_connect("localhost", "username", "password");
    mysql_select_db("my_database");
    $query = mysql_query("SELECT id, name, country FROM test_users");
    
    The mysql_query() function simply sends the SQL code to the MySQL server and then returns a link to the result. We will then have to use one of the many related PHP functions to actually use the result. For instance, we can see how many rows were returned by using the mysql_num_rows() function (the connection should already be made, as shown above):
    $query = mysql_query("SELECT id, name, country FROM test_users");
    echo "The table currently contains " . mysql_num_rows($query) . " row(s)";
    
    Of course, if we only wanted the number of rows, there would be more efficient ways of doing it and there would be no reason for selecting all three rows. Instead of just getting the number of rows, let's try actually getting some data out:
    $query = mysql_query("SELECT id, name, country FROM test_users");
    echo "The first name is: " . mysql_result($query, 0, "name");
    
    The mysql_result() can pick out a single piece of data from a result link. As parameters, we specify the query link, the row index and the name of the column we want data for, so in this case we get a result from the $query result reference, we use the first row of returned (row number zero) and we get data from the column called "name". That will get us the first name in the table, which is then outputted.

    In most situations you might need all the rows of data that you select, along with all the columns you select. This is usually done with the mysql_fetch_array() function, which simply gets you an entire row of data as an array, while moving the internal pointer one step ahead, so that the function will get you the row after that the next time you call it. This makes it excellent for using with a loop, to get all the rows one after another. Let's look at an example where we do just that:
    $query = mysql_query("SELECT id, name, country FROM test_users");
    while($row = mysql_fetch_array($query))
        echo $row["name"] . " is from " . $row["country"] . "<br />";
    
    We use a while loop, in which we assign the result of the mysql_fetch_array() function to the variable named $row on each iteration. This works because mysql_fetch_array() will return FALSE when there are no more rows, in which case the while loop will end. As long as there IS in fact a row left, mysql_fetch_array() places all columns and their values in the $row variable, where we can access it from simply by asking for the same name used in the SQL code. In our example, that gives us access to id, name and country, but to keep it less complicated, I have only used name and country so far.

    So, that's the most basic ways of getting data out of the database. As you can see, it's fairly easy, since PHP has a bunch of nice functions for doing it, but there's much more to working with MySQL and there's definitely more to writing SQL. Read on to learn more about both.


    MySQL and the WHERE part

    In the previous chapter, we saw how we could use the SELECT query to get data from the database, but we weren't exactly very picky about which data to get. As you will realize in the following chapters, the SELECT statement is very powerful and allows you to do pick, prioritize and sort your data in all sorts of way before returning it. In this chapter we will have a look at the WHERE part, which allows you to decide which data to select.

    An SQL statement with a WHERE part could look like this:

    SELECT id, name, country FROM test_users WHERE id > 3

    You can of course set more than one criteria:

    SELECT id, name, country FROM test_users WHERE id > 3 AND id < 8

    And you can use strings as criteria as well:

    SELECT id, name, country FROM test_users WHERE country = 'USA'

    You can even use MySQL's own functions in the WHERE part. For instance like this, where we use the SUBSTRING() function in MySQL to get all users starting with the letter "S":

    SELECT id, name, country FROM test_users WHERE SUBSTRING(name, 1, 1) = 'S'

    To test the examples above, you can use this test code we wrote in a previous chapter. Simply put one of the queries inside the mysql_query() function and run the code:
    mysql_connect("localhost", "username", "password");
    mysql_select_db("my_database");
    
    $query = mysql_query("Insert your SQL query here");
    while($row = mysql_fetch_array($query))
        echo $row["name"] . " is from " . $row["country"] . "<br />";
    



    MySQL and the ORDER BY part

    In the previous chapter, we used the WHERE part of an SQL query to decide which rows we wanted to SELECT. In this chapter, we will look into sorting the result, to get the data out in a specific order. In MySQL, as in most other SQL dialects, the keyword used to sort data is ORDER BY. Let's jump straight to an example:

    SELECT name, country FROM test_users ORDER BY name

    The ORDER BY is followed by the column we wish to sort by. In this example, we get our users sorted alphabetically by their name. The default order is from small to big, or in the case of strings, from A to Z, known as ascending order. In other words, the above example could also look like this:

    SELECT name, country FROM test_users ORDER BY name ASC

    But since it's the default order, it's optional. If you want from big to small or Z to A, we want it in descending order, for which we use the DESC keyword:

    SELECT name, country FROM test_users ORDER BY name DESC

    In some cases, it can be very useful to sort by more than one column. For instance, you may want to sort by country first, and name secondly. The syntax is the same, you just separate the columns you wish to sort by with a comma, like this:

    SELECT name, country FROM test_users ORDER BY country, name

    In this case, users will be ordered by the name of their country first, and people from the same country will be ordered by their own name. You can even use different sorting directions for each of the columns, like this:

    SELECT name, country FROM test_users ORDER BY country ASC, name DESC

    To test the examples above, you can use this test code we wrote in a previous chapter. Simply put one of the queries inside the mysql_query() function and run the code:
    mysql_connect("localhost", "username", "password");
    mysql_select_db("my_database");
    
    $query = mysql_query("Insert your SQL query here");
    while($row = mysql_fetch_array($query))
        echo $row["name"] . " is from " . $row["country"] . "<br />";
    



    MySQL and the LIMIT part

    Sometimes you only need a limited number of rows from a table, for instance because you want pagination, where data are divided into pages with a specific number of rows on each page. In MySQL, you can limit the amount of rows returned with the LIMIT keyword. Here's an example:

    SELECT name, country FROM test_users LIMIT 3

    This query will return the first 3 rows in the table, but in most cases, you would want to order the data, to get the first rows based on a specific sort order. Fortunately, we learned about the ORDER BY keyword in the previous chapter, so here's an example where we combine them:

    SELECT name, country FROM test_users ORDER BY country LIMIT 3

    This will give us the first 3 rows, but based on the country name instead of the default sorting order in the table, which is usually the primary key. The LIMIT keyword is followed by one or two parameters. If there's only one, it will be used to control the amount of rows returned, but if you specify two parameters, the first will be used to control the starting row, while the second parameter becomes the amount of rows returned. Here's an example:

    SELECT name, country FROM test_users ORDER BY country LIMIT 1, 3

    This query will get 3 rows, starting with the secondary row, ordered by country name. You might think that the first number should be 2 instead of 1, to start from the secondary row, but the LIMIT keyword is zero-index based, which means that counting starts from 0 instead of 1. So to start from the first row, you would specify 0 (which is of course the default value), 1 to start from the second row, 2 to start from the third row and so on.

    To test the examples above, you can use this test code we wrote in a previous chapter. Simply put one of the queries inside the mysql_query() function and run the code:
    mysql_connect("localhost", "username", "password");
    mysql_select_db("my_database");
    
    $query = mysql_query("Insert your SQL query here");
    while($row = mysql_fetch_array($query))
        echo $row["name"] . " is from " . $row["country"] . "<br />";
    



    Handling MySQL errors

    When using PHP and MySQL together, you will likely run into a situation where you've made some sort of error in your SQL query, like misspelling a column name or a keyword or something like that. By default, PHP will not show you exactly what the problem is, only that you wrote a query which is not entirely correct. Let's try writing a faulty query to see the response from PHP:
    $query = mysql_query("SELECT id, namme FROM test_users");
    while($row = mysql_fetch_array($query))
        echo $row['id'] . " - " . $row["name"] . " is from " . $row["country"] . "<br />";
    
    This is the example we are using a lot in this part of the tutorial, but in this case, we have misspelled the name column to provoke an error, which we get:

    Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in test.php on line 7

    As you can see, the error is not thrown until we try using the resource returned by the mysql_query() function, which we do when we call the mysql_fetch_array() function, in my file located on line 7. The error is very generic and not very helpful. This is on purpose, because knowledge about your database structure makes your website more vulnerable to SQL injection attacks, a problem we will discuss later on.

    You might be able to spot the error and fix it in a lot of situations, but if not, you can use the mysql_error() function to get a bit more information abut the problem. This function simply returns any error returned from the last executed MySQL function. You should only use this function for finding and fixing problems, and then remove it again once the problem has been fixed. Here's the above example, but where we call the mysql_error() function to get more information:
    $query = mysql_query("SELECT id, namme FROM test_users");
    while($row = mysql_fetch_array($query))
        echo $row['id'] . " - " . $row["name"] . " is from " . $row["country"] . "<br />";
    echo mysql_error();
    
    This will give you a far more useful error message:

    Unknown column 'namme' in 'field list'

    Try making various errors in the SQL query and see the message that MySQL returns through the mysql_error() function, to see how it responds. This will help you identify SQL errors better in the future. The above one is very precise and easy to fix, while others can be a bit more cryptic to the untrained eye.
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