/**
  * Logs out a user with the given username and password POSTed. 
  *
  * @url POST /user/logout/
  */
 public function logout()
 {
     $agent = isset($_POST['agent']) ? $_POST['agent'] : "";
     $authUserId = parent::CheckAuthentication(false);
     if ($authUserId > 0) {
         $user = parent::UserById($authUserId);
         parent::AppendLog("logout", '', $agent, $user['Email']);
     }
 }