A simple tutorial Here we would like to show the very basics of PHP in a short, simple tutorial. This text only deals with dynamic web page creation with PHP, though PHP is not only capable of creating web pages. See the section titled What can PHP do for more information. PHP-enabled web pages are treated just like regular HTML pages and you can create and edit them the same way you normally create regular HTML pages.
Your first PHP-enabled page This tutorial assumes PHP is already installed. Installation instructions can be found on the download page. Create a file named hello.php with the following content: Our first PHP script: <filename>hello.php</filename> ]]> Using your terminal, navigate to the directory containing this file and start a development server with the following command: Use your browser to access the file with your web server's URL, ending with the /hello.php file reference. According to the previous command executed, the URL will be http://localhost:8000/hello.php. If everything is configured correctly, this file will be parsed by PHP and you will see the "Hello World!" output displayed in your browser. PHP can be embedded within a normal HTML web page. That means inside your HTML document you can write the PHP statements, as demonstrated in the following example: PHP Test Hello World

'; ?> ]]> This will result in the following output: PHP Test

Hello World

]]> This program is extremely simple and you really did not need to use PHP to create a page like this. All it does is display: Hello World using the PHP echo statement. Note that the file does not need to be executable or special in any way. The server finds out that this file needs to be interpreted by PHP because you used the ".php" extension, which the server is configured to pass on to PHP. Think of this as a normal HTML file which happens to have a set of special tags available to you that do a lot of interesting things. The point of the example is to show the special PHP tag format. In this example we used <?php to indicate the start of a PHP tag. Then we put the PHP statement and left PHP mode by adding the closing tag, ?>. You may jump in and out of PHP mode in an HTML file like this anywhere you want. For more details, read the manual section on the basic PHP syntax. A Note on Line Feeds Line feeds have little meaning in HTML, however it is still a good idea to make your HTML look nice and clean by putting line feeds in. A linefeed that follows immediately after a closing ?> will be removed by PHP. This can be extremely useful when you are putting in many blocks of PHP or include files containing PHP that aren't supposed to output anything. At the same time it can be a bit confusing. You can put a space after the closing ?> to force a space and a line feed to be output, or you can put an explicit line feed in the last echo/print from within your PHP block. A Note on Text Editors There are many text editors and Integrated Development Environments (IDEs) that you can use to create, edit and manage PHP files. A partial list of these tools is maintained at PHP Editors List. If you wish to recommend an editor, please visit the above page and ask the page maintainer to add the editor to the list. Having an editor with syntax highlighting can be helpful. A Note on Word Processors Word processors such as StarOffice Writer, Microsoft Word and Abiword are not optimal for editing PHP files. If you wish to use one for this test script, you must ensure that you save the file as plain text or PHP will not be able to read and execute the script. Now that you have successfully created a working PHP script, it is time to create the most famous PHP script! Make a call to the phpinfo function and you will see a lot of useful information about your system and setup such as available predefined variables, loaded PHP modules, and configuration settings. Take some time and review this important information. Get system information from PHP ]]>
Something Useful Let us do something more useful now. We are going to check what sort of browser the visitor is using. For that, we check the user agent string the browser sends as part of the HTTP request. This information is stored in a variable. Variables always start with a dollar-sign in PHP. The variable we are interested in right now is $_SERVER['HTTP_USER_AGENT']. $_SERVER is a special reserved PHP variable that contains all web server information. It is known as a superglobal. See the related manual page on superglobals for more information. To display this variable, you can simply do: Printing a variable (Array element) ]]> A sample output of this script may be: There are many types of variables available in PHP. In the above example we printed an element from an Array variable. Arrays can be very useful. $_SERVER is just one variable that PHP automatically makes available to you. A list can be seen in the Reserved Variables section of the manual or you can get a complete list of them by looking at the output of the phpinfo function used in the example in the previous section. You can put multiple PHP statements inside a PHP tag and create little blocks of code that do more than just a single echo. For example, if you want to check for Firefox you can do this: Example using <link linkend="language.control-structures">control structures</link> and <link linkend="language.functions">functions</link> ]]> A sample output of this script may be: Here we introduce a couple of new concepts. We have an if statement. If you are familiar with the basic syntax used by the C language, this should look logical to you. Otherwise, you should probably pick up an introductory PHP book and read the first couple of chapters, or read the Language Reference part of the manual. The second concept we introduced was the str_contains function call. str_contains is a function built into PHP which determines if a given string contains another string. In this case we are looking for 'Firefox' (so-called needle) inside $_SERVER['HTTP_USER_AGENT'] (so-called haystack). If the needle is found inside the haystack, the function returns true. Otherwise, it returns &false;. If it returns &true;, the if expression evaluates to &true; and the code within its {braces} is executed. Otherwise, the code is not run. Feel free to create similar examples, with if, else, and other functions such as strtoupper and strlen. Each related manual page contains examples too. If you are unsure how to use functions, you will want to read both the manual page on how to read a function definition and the section about PHP functions. We can take this a step further and show how you can jump in and out of PHP mode even in the middle of a PHP block: Mixing both HTML and PHP modes

str_contains() returned true

You are using Firefox

str_contains() returned false

You are not using Firefox

]]> A sample output of this script may be: str_contains() returned true

You are using Firefox

]]> Instead of using a PHP echo statement to output something, we jumped out of PHP mode and just sent straight HTML. The important and powerful point to note here is that the logical flow of the script remains intact. Only one of the HTML blocks will end up getting sent to the viewer depending on the result of str_contains. In other words, it depends on whether the string Firefox was found or not.
Dealing with Forms One of the most powerful features of PHP is the way it handles HTML forms. The basic concept that is important to understand is that any form element will automatically be available to your PHP scripts. Please read the manual section on Variables from external sources for more information and examples on using forms with PHP. Here is an example HTML form: A simple HTML form ]]> There is nothing special about this form. It is a straight HTML form with no special tags of any kind. When the user fills in this form and hits the submit button, the action.php page is called. In this file you would write something like this: Printing data from our form . You are years old. ]]> A sample output of this script may be: Apart from the htmlspecialchars and (int) parts, it should be obvious what this does. htmlspecialchars makes sure any characters that are special in html are properly encoded so people can't inject HTML tags or Javascript into your page. For the age field, since we know it is a number, we can just convert it to an int which will automatically get rid of any stray characters. You can also have PHP do this for you automatically by using the filter extension. The $_POST['name'] and $_POST['age'] variables are automatically set for you by PHP. Earlier we used the $_SERVER superglobal; above we just introduced the $_POST superglobal which contains all POST data. Notice how the method of our form is POST. If we used the method GET then our form information would live in the $_GET superglobal instead. You may also use the $_REQUEST superglobal, if you do not care about the source of your request data. It contains the merged information of GET, POST and COOKIE data.
What's next? With your new knowledge you should be able to understand most of the manual and also the various example scripts available in the example archives. To view various slide presentations that show more of what PHP can do, see the PHP Conference Material Site: &url.php.talks;