private static function conversionRoutingCode($zipcode) {
        $number = $zipcode;
        switch (strlen($zipcode)) {
            case 11:
                $number = bcadd($number, '1000000000', 0);
            case 9:
                $number = bcadd($number, '100000', 0);
            case 5:
                $number = bcadd($number, '1', 0);
            default:
                return $number;
        }
    }