/**
  * Using singleton pattern we can access session anywhere in the app
  * HTTPSession->getInstance() will return the only instance created in init.php
  * @return HTTPSession instance
  */
 public static function getInstance()
 {
     # If the session doesn't exist yet, created it
     if (!isset(HTTPSession::$instance)) {
         HTTPSession::$instance = new HTTPSession();
     }
     return HTTPSession::$instance;
 }