One thing that causes a lot of problems still right now is the lack of pre-compiled packages for Linux distributions. Between that and users who would just want to compile their own anyway I get a lot of questions about how to setup a system for, and compile, PHP-GTK2. Personally, I get a bit weary of repeating the same instructions over and over, so I have turned out a work-in-progress guide to compiling PHP-GTK2 on Unix systems with notes aimed to help people on certain distributions.
Also up on my site I have begun formatting some of my PHP-GTK2 Object Oriented tutorials for the web. I hope that these documents can help you get started and harness the full power of PHP-GTK.
Visit My Site for all sorts of tutorials or jump straight to the guide to compiling PHP-GTK2.