public function login($username, $password)
 {
     $db = Database::getInstance();
     $username = $db->escape_string($username);
     $password = $db->escape_string($password);
     $query = "SELECT uid, username, email, access_level FROM storex.users WHERE username = '******' AND password = MD5('{$password}')";
     $result = $db->getRow($query);
     if ($result) {
         $ss = SessionStorage::getInstance();
         $ss->set("user", $result);
         return session_id();
     } else {
         throw new AccessDeniedException("You are not allowed to login");
     }
     return $result;
 }
 public function __construct()
 {
     $this->db = Database::getInstance();
 }