What do I need?
In this tutorial we assume that your server has activated support for PHP 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 do not need to do anything. Just create your .php files, put them in your web directory and the server will automatically parse them for you. There is no need to compile anything nor do you need to install any extra tools.
Your first PHP-enabled page
Create a file named hello.php and put it in your web server's root directory (DOCUMENT_ROOT) with the following content:
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Use your browser to access the file with your web server's URL, ending with the "/hello.php" file reference. When developing locally this URL will be something like http://localhost/hello.php or http://127.0.0.1/hello.php but this depends on the web server's configuration. f everything is configured correctly, this file will be parsed by PHP and the following output will be sent to your browser:
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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.
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. Get system information from PHP:
(); ?> |
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 an autoglobal (or superglobal).
Example 2-3. Printing a variable (Array element)
echo $_SERVER['HTTP_USER_AGENT']; ?> |
A sample output of this script may be:
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) |
