Before you can start implementing PHP scripts on your web site you first need to check whether your web host supports PHP. The information that the host makes available to you may tell you this but the easiest way to find out is to actually test it for yourself. To do this you create a new text document called phpinfo.php and insert the following code into it:
<?php phpinfo(); ?>
You then need to upload this file to your site using ftp (or whatever other method that you usually use to upload files). You now type in the address of this file into your browser address bar (ie. if your web address is http://www.mysite.com you would go to http://www.mysite.com/phpinfo.php).
You will see one of two things. Either the file will be interpreted as text and you will see the same text that you typed in (in which case you can't use PHP) or you will see a nicely formatted web page starting with PHP Version at the top and with lots of information about the PHP configuration of your web host below it.
The information on this page is very useful when it comes to configuring PHP scripts to run on your hosting service. To make it easier to find out this info when I am not online, I saved the page (with a .htm suffix) onto my own computer so that I can refer to it while working on scripts when not connected to the internet.
This article written by Stephen Chapman, Felgall Pty Ltd.