Visit the Official PHP Website
By James N Hitz
What is PHP?
PHP is a server-side HTML Preprocessor that is HTML-embedded. Under normal cirumstances, your web browser sends GET instructions to the web server which then coughs up a web page in "plain HTML" for your browser to display. This is the normal setting!
PHP changes things a little bit. When your browser makes a GET request for a PHP document, instead of the server just coughing up the page, it gives it up to the PHP pre-processor that does some magic with it and then gives it back to the server. The server then coughs (it actually vomits this time around) the page to you as though it were plain HTML. The server behaves as if nothing happenned and takes all the glory. Lying infidel!
Wait a minute! Just how did the server identify the file as a PHP document and not just a normal HTML file? PHP files are given a special file-extension (.php .phtml or .php3). That way the server knows NOT to touch them until they have been processed by PHP and converted into HTML. Smart Huh?!
Be informed though, the server administrator may decide to set up another method for the web server to identify PHP scripts other than the standard .php and .php3. Mmmm.