//Controller for core:
public function indexAction()
    {
        $session = new Session();
        $session->start();

        if ($session->get('welcome_flag')=='0'){
            return $this->render('MarkCoreBundle:Default:index.html.twig');
        } else {
            return $this->redirect($this->generateUrl('welcome_homepage'));
        }
    }

//Controller for welcome:
public function indexAction()
    {
        $session = new Session();
        $session->start();

        if ($session->get('welcome_flag') == '0'){
            return $this->redirect($this->generateUrl('core_homepage'));
        } else {
            $session->set('welcome_flag', '0');
            return $this->render('MarkWelcomeBundle:Default:index.html.twig');
        }
    }