Fatal error: Call to a member function fetch() on a non-object in /home/fsasaewqx/public_html/admin/class/database.class.php on line 80

        $query = $this->_db->query("SELECT COUNT(id) as exist,sonErisimTarihi,yetkiler,password FROM admin WHERE admin='".$_SESSION["username"]."'")->fetch(PDO::FETCH_ASSOC);