php - db->insert_id() Always Equals Zero -

i have ajax function in controller:

public function add_display_row($shape, $rows) {         $newrecord = array(             'work_id' => '',             'section_id' => (int)$rows + 1,             'shape' => $shape         );          //insert new record after last         $newro = array();         for( $c=1; $c<6; $c++){             $newrecord['ordinal'] = $c;             $newrecord['size_id'] = $this->work_model->get_size_from_specs($shape, $c);             $insnew = $this->work_model->save_new_featured_shape($newrecord);             $newrecord['item_id'] = $insnew;             array_push($newro, $newrecord);         }          print_r($newro);     } 

and in model

public function save_new_featured_shape($record) {       $this->db->trans_begin();       $this->db->insert('work_featured', $record);        if ($this->db->trans_status() === false) {         $this->db->trans_rollback();         return false;       } else {         $this->db->trans_commit();         $insert_id = $this->db->insert_id();         return $insert_id;       }     } 

after 5 records inserted, returning array caller , item_id (which should insert id of each) equals 0.

i need insert_id returned build dom element insert dom.

can see why zero?

modify add_display_row following.

   public function add_display_row($shape, $rows) {     //$this->load->model('work_model');     $newrecord = array(         'work_id' => '',         'section_id' => (int)$rows + 1,         'shape' => $shape     );     $new_arr=array();     //insert new record after last     $newro = array();     for( $c=1; $c<6; $c++){         $newrecord['ordinal'] = $c;         $newrecord['size_id'] =  $this->work_model->get_size_from_specs($shape, $c);         $insnew = $this->save_new_featured_shape($newrecord);         $new_arr['item_id'] = $insnew;         $new_arr_arr=array_merge($newrecord,$new_arr);         array_push($newro, $new_arr_arr);     }     echo "<pre>";     print_r($newro);     } 

and model function following.

  public function save_new_featured_shape($record) {   $this->db->trans_begin();   $this->db->insert('work_featured', $record);     $insert_id = $this->db->insert_id();   if ($this->db->trans_status() === false) {     $this->db->trans_rollback();     return false;   } else {     $this->db->trans_commit();      return $insert_id;   } }