I can't find a good use (i know there is) for php... All I can use it for are forms that submit to your email.. what else? and how complex?
One real good use for php is what is referred to as includes. Here is an article that tells all about it PHP Includes
Well pretty much every website one the net uses some sort of Server Side Scripting Language PHP being one of the most common. PHP shows its strength by being able to interact with a database (unlink HTML) thus allowing for dynamic sites.