function _execute($sql)
 {
  $sql = $this->_prep_query($sql);
  $result = @mysqli_query($this->conn_id, $sql);
  return $result;
 }

 function _execute($sql)
 {
  @mysqli_free_result($this->result_id);

  $sql = $this->_prep_query($sql);
  $retval = @mysqli_multi_query($this->conn_id, $sql);
  $firstResult = @mysqli_store_result($this->conn_id);

  while(@mysqli_more_results($this->conn_id)){   
   if (@mysqli_next_result($this->conn_id))
   {
    $result = @mysqli_use_result($this->conn_id);
    @mysqli_free_result($result);
   }
  }

  if( !$firstResult && !@mysqli_errno($this->conn_id)){
   return true;
  }

  return $firstResult;
 }