CI_DB_active_record::insert PHP Method

    function insert($table = '', $set = NULL)
    {
        if (!is_null($set)) {
            $this->set($set);
        }
        if (count($this->ar_set) == 0) {
            if ($this->db_debug) {
                return $this->display_error('db_must_use_set');
            }
            return FALSE;
        }
        if ($table == '') {
            if (!isset($this->ar_from[0])) {
                if ($this->db_debug) {
                    return $this->display_error('db_must_set_table');
                }
                return FALSE;
            }
            $table = $this->ar_from[0];
        }
        $sql = $this->_insert($this->_protect_identifiers($table, TRUE, NULL, FALSE), array_keys($this->ar_set), array_values($this->ar_set));
        $this->_reset_write();
        return $this->query($sql);
    }

 protected function _set($key, $data, $group, $tenant_id, $expires = null)
 {
     if (empty($expires)) {
         $expires = $this->default_expires;
     }
     $data = $this->_serialize(array('data' => $data, 'expires' => time() + intval($expires)));
     $this->_delete($key, $group, $tenant_id);
     $r = $this->_db->insert($this->_table, array($this->_table . '.key' => $key, $this->_table . '.group' => $group, $this->_table . '.value' => $data, $this->_table . '.tenant_id' => $tenant_id));
     return $this->_db->affected_rows() > 0;
 }