Tulip IDE is a PHP IDE made in PHP-GTK and initiated aroun 2004 as an all-PHP solution to produce PHP code. It allows connections to databases and CVS directories, as well as color-syntaxing, documentation linking, etc.
It's been inactive for a while now though, but might still be useful for anyone thinking about starting a new project of this kind (PHP-GTK 2 is out)
These details are provided for information only. No information here is legal advice and should not be used as such.