does anyone here know and use PHP in designing web pages?
if yes, what do you use for writing the code, where di you learn it, how long did it take?

I use dreamweaver, but i write the code myself. i use it because it's easier to find a part of the code in it than in notepad because of the different colours...
i learned it by reading the tutorials, designing a web page while reading them. it didn't take more than a week or two i think. I'm not sayin i memorized every single syntax or anything, but i did learn how it's supposed to look and what are the most common things i should bare in mind at all times

I currently use Ajax programming codes in PHP web designing scripts. Ajax is used to make the web page more lively and interactive.

Could someone give me a detailed description of what PHP entails? I have head much about it but do not know what it really is.

Wikipedia has somewhat detailed description.
http://en.wikipedia.org/wiki/PHP