Braintree\TransactionGateway::_validateId PHP Method

    private function _validateId($id = null)
    {
        if (empty($id)) {
            throw new InvalidArgumentException('expected transaction id to be set');
        }
        if (!preg_match('/^[0-9a-z]+$/', $id)) {
            throw new InvalidArgumentException($id . ' is an invalid transaction id.');
        }
    }