What is it?
PHP-GTK is an extension for PHP, which enables you to write real applications with a GTK-interface. This works really well on the OpenMoko, and some applications has already been written.
How to get it?
Derick Rethans has ported PHP and PHP-GTK for the OpenMoko, which you can read more about on his blog in this post.
There has already been set up a repository called Knjrepository by Kasper Johansen, which includes these packages amongst many others.