php - codeigniter dynamic field added on migration time -

i have 2 database called "migrate_new" , "migrate_old" , both have 1 table called "cms_pages".

i want compare "migrate_old" db "cms_pages" "migrate_new" "cms_pages" table structure if "migrate_new" database "cms_pages" not have "field" alter table automatically.

below code compare "migrate_old" "cms_pages" fields not in "migrate_new" "cms_pages" want add fields on table. want continue process in place of exit.

**> 1 can have idea add fields automatically no need stop migration task?

i not able field details type , key , etc. how know alter table use modify or add fields. short want set structure out loss of data automatically. in advance..
**

    $this->load->database();     $admin_db = $this->load->database('admindb', true);      $query = $this->db->get('cms_page');     $result = $query->result();      $fields_old = $this->db->list_fields('cms_page'); //  $fields_new = $admin_db->list_fields('cms_page');     $flag = false;     foreach ($fields_old $field){          if (!$admin_db->field_exists($field, 'cms_page'))         {             echo $field.'=> not exists in new table please contact developer <br>';             $flag = true;         }     }      if($flag){         exit;                }