You should find here some infos about PHP which I started to learn mid-2004, out of real, old interest, and because I found a number of job offers needing to know this language... Buying Code(r) HS#3 (a French magazine about programming) dedicated to PHP helped me to jump start.
Still, I have to remember some peculiarities, like the strange variable and function visibility... And I have to survey the impressive set of functions. Even limiting myself to base functions (avoiding libraries like GD or cURL), it is quite some work!
I improved this PHP program to make it usable and to start manipulating PHP. You can see a page on it, explaining why I changed it and what improvements I made.
A very nice PHP framework, which I chose after looking at dozens of similar projects. It is PHP4 compatible (important), well written, using sane principles (OOD, MVC, design patterns.
I used it to create the e-commerce site Atopic & Pictogram, and I contributed back some improvements.