php.net is good as a reference guide, for checking on functions & what they do, how to use them, etc. It's not the best of places to start if you don't have much other coding experience and aren't used to reading that kind of documentation.
Some good tutorial-style sites you may wish to have a look at are:
http://www.phpbuilder.com/
http://www.sitepoint.com/subcat/php-tips
Oh, and always have the manual bookmarked, just in case!
http://www.php.net/manual/en/
Probably a good idea to get a book on the subject too, even if it's just one of the '24 hours..' titles, so you don't need to be stuck behind a monitor for both reading theory & coding examples.