Symfony2无法启动会话：已由PHP启动

[2014-11-06 11:21:13] request.INFO: Matched route "core_timetracking_new_user" (parameters: "_controller": "Bricks\Custom\CoreBundle\Controller\TimeTrackingController::newuserAction","_route": "core_timetracking_new_user") [] []
[2014-11-06 11:21:13] request.CRITICAL: Uncaught PHP Exception RuntimeException: "Failed to start the session: already started by PHP." at /var/cache/app/prod/classes.PHP line 113 {"exception":"[object] (RuntimeException: Failed to start the session: already started by PHP. at /var/cache/app/prod/classes.PHP:113)"} []

奇怪的是我没有开始会话或使用它,继承人控制器代码：

/**
 * @View
 */
public function newuserAction()
{
    $trackingservice=$this->get('core.timetracking_service');
    $user= new TimeTrackingUser();
    $request=$this->getrequest();

    $form = $this->createFormBuilder($user)
        ->add('name','text')
        ->add('email','text')
        ->add('pass','password')
        ->add('save','submit',array('label' => 'Erstellen'))
        ->getForm();

    $form->handlerequest($request);

    if ($form->isValid()) {
        $trackingservice->persistuser($form->getData());
        return $this->redirect($this->generateUrl('core_timetracking_user_list'));
    }else {
        return array(
            'form' => $form->createView()
        );
    }
}

虽然这个动作很棒

/**
 * @View
 */
public function listuserAction()
{

    $request=$this->getrequest();
    $trackingservice=$this->get('core.timetracking_service');    
    $users=$trackingservice->getAllUsers();

    return array(
        'users' => $users
    );
}

所以唯一的区别是我使用

$form->handlerequest($request);

还检查了我的所有文件AppKernel等是否都以

两个动作(工作一个和不工作一个)都在同一个控制器中