#1 Highligter by file type

[Benjamin D. Smith]

Currently, I have a large-ish project using PHP-GTK. To
avoid name collisions with Adobe Photoshop (which uses
the .php file extension) all the files were renamed to
*.phpgtk.

This means, however, that the highligher does not treat
the file as a "php" file and renders everything as straight
black.

Can there be a way to associate a file *extension* with
a particular highligter format? Say, with a registry entry,
or a config file someplace?

Eternal thanks,

-Ben