Неправильно работает формирование URL - [VM1] Общие вопросы и ошибки

if (empty($flypage)) {
            $flypage = FLYPAGE;
        }
        $url_parameters = "index.php?page=shop.product_details&flypage=$flypage&product_id=" . $db_browse->f("product_id") . "&category_id=" . $db_browse->f("category_id");
        if( $manufacturer_id ) {
        	$url_parameters .= "&manufacturer_id=" . $manufacturer_id;
        }
        if( $keyword != '') {
        	$url_parameters .= "&keyword=".urlencode($keyword);
        }
        $url = $sess->url( $url_parameters );

 $url_parameters = "page=shop.product_details&flypage=$flypage&product_id=" . $db_browse->f("product_id") . "&category_id=" . $db_browse->f("category_id");

        $url_parameters = "index.php?page=shop.product_details&flypage=$flypage&product_id=" . $db_browse->f("product_id") . "&category_id=" . $db_browse->f("category_id");