public function doesUserExist()
 {
     try {
         $params = $this->getParams();
         $username = $params[0];
         $userModel = new UsersModel();
         $userExist = $userModel->userExist($username);
         $userExist = $userExist[0]['COUNT(username)'];
         $response = new AJAXAnswer();
         if (!$userExist) {
             $response->setSuccess(true);
         } else {
             $response->setSuccess(false);
         }
         $response->answer();
     } catch (\Exception $e) {
         $error = new AJAXAnswer(false, $e->getMessage());
         $error->answer();
     }
 }