All you need to programme in PHP is PHP: Hypertext Preprocessor the manual explains everything about each function which is all you really need to know, and do yourself a favour by turning on full error reporting in everyscript you write, will save you loads of time.
I'd recommend picking up a simple book like Sams Teach Yourself PHP in 24 hours. That was the first book I ever read and then look through the online manuals. By then you should be able to get started pretty well.