How to Register File Types?

[mcrbids]

I'm attempting to write an installer for a php-gtk program. I've figured out most of it, except that I need to register the ".php" filetype with the correct executable so that the application will actually run.

I can't find this anywhere in the documentation... how do I do this?

I want to register the ".php" filetype with application

c:\Program Files\php4\php_gtk.exe

Thanks!