Xây dưng function lastAffected, lastError 9.4 (Ok)

public function lastAffected($source = null) {
      if ($this->_result) {
        return mysqli_affected_rows($this->connection);
      }
      return null;
    }
    public function lastError() {
      if (mysqli_errno($this->connection)) {
        return mysqli_errno($this->connection) . ': ' . mysqli_error($this->connection);
      }
      return null;
    }