second "manufacturer" sidebox: almost finished... and stuck!

A second dop-down menu to filter with a "manufacturer2" field to add a second filter.

Basically, it's just a question a duplicating every occurence of manufacturer_id throughout the entire fileset (creating some manufacturer2.php extra files is necessary) and of course create extra fileds and tables for manufacturer2 and manufacturer2 info.

Seemed like a piece of cake project, but turned into much more fun than expected ;-)

I've been working for 2 days on it, I'm almost done and stuck on the following:

I need help on the includes/index_filters/default_filter.php

Here is my file in txt format: http://www.malleryhall.com/default_filter.txt

when I select a "manufacturer" in the second menu, I'm sent back to the homepage, despite the fact that my url has the following structure:

main_page=index&manufacturers2_id=12

Thanks for your help!

I figured out it was easier to hijack the existing filters of the "product music" type: I turned "music genre" into "item type" and "record company" into manufacturer, and it works like a charm for the furiture store I'm designing.