I've just uploaded into the bryght svn a basic filter, actually a couple of them (I was lazy). They parse a php file, and output (leave out in the case of the no_filter), all functions starting with a given prefix.

I've done it in order to be able to play with separate theme_xxx files.

usage:
vlado:~$ no_filter function_prefix php_file
read the php_file, print it to stdout, leaving out all functions starting with function prefix.

vlado:~$ yes_filter function_prefix php_file
read the php_file, print it to stdout, leaving out all functions not starting with function prefix.

both filters know about associated comments, etc...