IBAN\Core\IBAN::local_bcmod PHP Метод

    private function local_bcmod($x, $y)
    {
        if (!function_exists('bcmod')) {
            $take = 5;
            $mod = '';
            do {
                $a = (int) $mod . substr($x, 0, $take);
                $x = substr($x, $take);
                $mod = $a % $y;
            } while (strlen($x));
            return (string) $mod;
        } else {
            return bcmod($x, $y);
        }
    }