Redirect if not loged in

1.module.config.php

return array(
    'controllers' => array(
        'initializers' => array(
                function ($instance, $serviceManager) {
                    if ($instance instanceof NeedLoginAwareInterface) {
                        $auth = $serviceManager->getServiceLocator()->get('cwdAdmin.auth_service');
                        if(!$auth->hasIdentity()) {
                            //$instance->redirect()->toUrl('/admin/auth/login');
                            header('Location: /auth/login');
                            exit;
                        }
                    }

                }
        )
    )
);

2.Controller.php

class MyController extends Controller implements NeedLoginAwareInterface
{
     public function indexAction()
     {
          // only displayed if we have an identity
     }
}

3.interface.php

namespace Foo;

interface NeedLoginAwareInterface
{

}