PHP-GTK users can now rejoice (or even those that want to become PHP-GTK users)! According to Scott Mattocks (the author), the PHP-GTK book is now available.
Pro PHP-GTK is now available. Pro PHP-GTK was written to provide the reader with an understanding of the fundamentals of PHP-GTK. This approach empowers the user with the ability to create applications not by just copying and modifying the examples but by understanding what tools are available to solve a problem and how different pieces of the puzzle work together.
The book goes into the details of parent and child relationships, signals and events, layout, displaying and collecting different types of data and customizing the look and feel of an application.
Scott also includes links to a table of contents [pdf] for the book and a sample chapter for those wanting to try before you buy.