Mimicing $_GET['main_page']

[retched]

You can do it without cPath, but that may cause SEO complications with canonical URLs.

Okay so here's what I have so far:

    if(isset($_GET['ufs'])) {
        $ufs = $_GET['ufs'];
        // First let's "fix" the search symbol.
        // Any sort of %20 and etc are already removed by PHP, so there is no need to run it a second time.
        // Let's remove any Underscores (as this will be a valid shortcut such as SPECIAL_X or DS01_20)
        $ufs = strtoupper(str_replace("_", " ", $ufs));

        $ufs_query = "SELECT ufs.products_id, master_categories_id FROM " . TABLE_CARDS_UFS . " ufs LEFT JOIN " . TABLE_PRODUCTS . " p ON ufs.products_id = p.products_id WHERE collector_no = '" . $ufs . "' LIMIT 1";
        $ufs_get_result = $db->Execute($ufs_query);

        $ufs_id = $ufs_get_result->fields['products_id'];
        $category_id = $ufs_get_result->fields['master_categories_id'];

        if($ufs_id && $category_id) {
            // Okay we have a valid result... Let's do a redirect.
            zen_redirect(zen_href_link("product_cards_ufs_info", 'cPath=' . zen_get_generated_category_path_rev($category_id) . '&products_id=' . $ufs_id, 'NONSSL'), 307);
        } else { // We didn't find a valid result... so redirect them to page not found OR homepage.
            if (MISSING_PAGE_CHECK == 'On' || MISSING_PAGE_CHECK == 'true') {
                zen_redirect(zen_href_link(FILENAME_DEFAULT));
            } else if (MISSING_PAGE_CHECK == 'Page Not Found') {
                zen_redirect(zen_href_link(FILENAME_PAGE_NOT_FOUND));
            }
        }
    } 

(Obviously TABLE_CARDS_UFS is defined in a separate define.)

My problem right now is:

zen_redirect(zen_href_link(FILENAME_PAGE_NOT_FOUND)); 

I'm trying to use the redirect code 404 but for some reason when I use:

zen_redirect(zen_href_link(FILENAME_PAGE_NOT_FOUND), 404); 

I get a blank page. Any sugestions?