ben bu hatayı alıyorum

Catchable fatal error: Object of class __PHP_Incomplete_Class could not be converted to string in user.php on line 248 this is the line

  function loadUser($userID)
  {
  global $db;   
    $res = $db->getrow("SELECT * FROM `{$this->dbTable}` WHERE `{$this->tbFields['userID']}` = '".$this->escape($userID)."' LIMIT 1");
    if ( !$res )
        return false;
    $this->userData = $res;
    $this->userID = $userID;
    $_SESSION[$this->sessionVariable] = $this->userID;
    return true;
  }

görmek

var_dump($_SESSION); 

array(1) { ["user"]=> &object(__PHP_Incomplete_Class)#1 (12) { ["__PHP_Incomplete_Class_Name"]=> string(11) "jooria_user" ["dbTable"]=> string(5) "users" ["sessionVariable"]=> string(4) "user" } }