I've been developing a PHP-GTK application over the past few months and have found that there are very few resources out there to help (the entire project seems a bit dead tbh..), however I have come across a few invaluable things that I thought I'd share:
php-gtk2 Cookbook: This is by far the best resource I have found. It has loads of examples and you can even look them up by widget type. It also has a help forum full of useful answers.
You have to register to see all of the code but it's free and I haven't had any spam as a result so I highly recommend it.
Official API documentation: This is a bit feeble but contains all the classes and methods (even if it doesn't explain them very well).
One thing to watch out for with this is that the class pages don't show you inherited methods (even from interfaces) so you have to read through the entire hierarchy to get the full picture.
Glade UI Designer: A handy tool for constructing interfaces for GTK. These produce an XML file which you can then read into your PHP code with the GTKBuilder class. Much nicer than having to create all of your interfaces in code.
Be wary though that it is a bit flakey (crashes sometimes) and it can only do so much for you, some of it will still need to be done in code.
When looking for other resources remember that GTK isn't specific to PHP and so you may find more results for just searching for GTK stuff.
Hope that helped!
