private function initHandler(SaveHandlerInterface $handler)
    {
        return session_set_save_handler(array($handler, 'open'), 
                                        array($handler, 'close'), 
                                        array($handler, 'read'), 
                                        array($handler, 'write'), 
                                        array($handler, 'destroy'), 
                                        array($handler, 'gc'));
    }