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 webpage creation with PHP, though PHP is not only capable of creating webpages. 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. What do I need? In this tutorial we assume that your server has support for PHP activated and that all files ending in .php are handled by PHP. On most servers this is the default extension for PHP files, but ask your server administrator to be sure. If your server supports PHP then you don't need to do anything. Just create your .php files and put them in your web directory and the server will magically parse them for you. There is no need to compile anything nor do you need to install any extra tools. Think of these PHP-enabled files as simple HTML files with a whole new family of magical tags that let you do all sorts of things. Your first PHP-enabled page Create a file named hello.php under your webserver root directory with the following content: Our first PHP script: <filename>hello.php</filename> PHP Test "; ?> ]]> The output of this script will be: PHP Test Hello World

]]> Note that this is not like a CGI script. The file does not need to be executable or special in any way. Think of it as a normal HTML file which happens to have a set of special tags available to you that do a lot of interesting things. This program is extremely simple and you really didn't need to use PHP to create a page like this. All it does is display: Hello World using the PHP echo statement. If you tried this example and it didn't output anything, or it prompted for download, or you see the whole file as text, chances are that the server you are on does not have PHP enabled. Ask your administrator to enable it for you using the Installation chapter of the manual. If you want to develop PHP scripts locally, see the downloads section. You can develop locally on any Operating system, be sure to install an appropriate web server too. 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 all you want. Something Useful Let's do something a bit more useful now. We are going to check what sort of browser the person viewing the page is using. In order to do that we check the user agent string that the browser sends as part of its 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"]. PHP Autoglobals Note $_SERVER is a special reserved PHP variable that contains all web server information. It's known as an Autoglobal. See the related manual page on Autoglobals (also known as Superglobals) for more information. These special variables were introduced in PHP 4.1.0. Before this time, we used the older $HTTP_*_VARS arrays instead, such as $HTTP_SERVER_VARS. Although deprecated, these older variables still exist. To display this variable, we can simply do: Printing a variable (Array element) ]]> A sample output of this script may be: Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0) There are many types of variables available in PHP. In the above example we printed an Array element. Arrays can be very useful. $_SERVER is just one variable that's automatically made available to you by PHP. A list can be seen in the Reserved Variables section of the manual or you can get a complete list of them by creating a file that looks like this: Show all predefined variables with <function>phpinfo</function> ]]> If you load up this file in your browser you will see a page full of information about PHP along with a list of all the variables available to you. 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 we wanted to check for Internet Explorer we could do something like this: Example using <link linkend="control-structures">control structures</link> and <link linkend="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. If you don't know enough C or some other language where the syntax used above is used, you should probably pick up any introductory PHP book and read the first couple of chapters, or read the Language Reference part of the manual. You can find a list of PHP books at &url.php.books;. The second concept we introduced was the strstr function call. strstr is a function built into PHP which searches a string for another string. In this case we are looking for "MSIE" inside $_SERVER["HTTP_USER_AGENT"]. If the string is found, the function returns &true; and if it isn't, it returns &false;. If it returns &true;, the if statement evaluates to &true; and the code within its {braces} is executed. Otherwise, it's not. Feel free to create similar examples, with if, else, and other functions such as strtoupper and strlen. Each related manual page contains examples too. 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

strstr must have returned true

You are using Internet Explorer

strstr must have returned false

You are not using Internet Explorer
]]> A sample output of this script may be: strstr must have returned true
You are using Internet Explorer
]]> 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 if strstr returned &true; or &false; In other words, if the string MSIE 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 in a form will automatically be available to your PHP scripts. Please read the manual section on Variables from outside of PHP for more information and examples on using forms with PHP. Here's an example HTML form: A simple HTML form Your name: Your age: ]]> 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 have something like this: Printing data from our form . You are years old. ]]> A sample output of this script may be: It should be obvious what this does. There is nothing more to it. The $_POST["name"] and $_POST["age"] variables are automatically set for you by PHP. Earlier we used the $_SERVER autoglobal, now above we just introduced the $_POST autoglobal 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 autoglobal instead. You may also use the $_REQUEST autoglobal if you don't care the source of your request data. It contains a mix of GET, POST, COOKIE and FILE data. See also the import_request_variables function. Using old code with new versions of PHP Now that PHP has grown to be a popular scripting language, there are more resources out there that have listings of code you can reuse in your own scripts. For the most part the developers of the PHP language have tried to be backwards compatible, so a script written for an older version should run (ideally) without changes in a newer version of PHP, in practice some changes will usually be needed. Two of the most important recent changes that affect old code are: The deprecation of the old $HTTP_*_VARS arrays (which need to be indicated as global when used inside a function or method). The following autoglobal arrays were introduced in PHP 4.1.0. They are: $_GET, $_POST, $_COOKIE, $_SERVER, $_ENV, $_REQUEST, and $_SESSION. The older $HTTP_*_VARS arrays, such as $HTTP_POST_VARS, still exist and have since PHP 3. External variables are no longer registered in the global scope by default. In other words, as of PHP 4.2.0 the PHP directive register_globals is off by default in &php.ini;. The preferred method of accessing these values is via the autoglobal arrays mentioned above. Older scripts, books, and tutorials may rely on this directive being on. If on, for example, one could use $id from the URL http://www.example.com/foo.php?id=42. Whether on or off, $_GET['id'] is available. For more details on these changes, see the section on predefined variables and links therein. What's next? With what you know now you should be able to understand most of the manual and also the various example scripts available in the example archives. You can also find other examples on the php.net websites in the links section: &url.php.links;.