Mr Mike Metcalf
How is PHP used?

PHP must first be installed on the server you wish to host your websites on. Visit php.org for more info. Next your HTML file must be renamed .php

Finally, PHP has a specific language and is inserted into HTML by use of . Example that prints "hello world" and uses a variable:

$toprint = "hello world";
print $toprint;
?>

You actually need to go to php.net not php.org

PHP is a server side language that can be used for a great deal of things on the web, including manipulating databases, files...etc.

If you're interested in getting some basic PHP knowledge try starting out here : http://www.w3schools.com/php/default.asp

You can also get some great tutorials here: http://phpfreaks.com. The forum there is a great place to get quick answers to your questions.

PHP code is enclosed in < ?php and ? >...like the person before me noted, you have to have PHP installed on your server (most host do have PHP installed, check with your host to be sure). It's a powerful tool that can do a lot.

I must say, your question is a bit vague. Do you have a certain thing you're trying to do or just wondering about PHP in general.