/**
  * Responds with an array of all user ID's
  */
 protected function get_users()
 {
     $offset = isset($_REQUEST['offset']) ? absint($_REQUEST['offset']) : 0;
     $role = isset($_REQUEST['role']) ? $_REQUEST['role'] : '';
     $users = $this->wizard->get_users($role, $offset);
     // send response
     $this->respond($users);
 }