insert_id not working

[eluser]Harold Villacorte[/eluser]
I just put this code in my current project and it works great:

Code:

public function insert_role ($post) {
  unset($post['add']);
  $query = $this->db->insert('roles', $post);
  $id = $this->db->insert_id();
  return ($id) ? $id : FALSE ;
}