title: FOS UserBundle server error when logout link hit
body: <p>I am new to the FriendsOfSymfony UserBundle and everything has been going well until I try to have a user logout.  The login works perfectly and I am using the basic configuration that I have seen on many sites. I only have 2 users that need to login. The problem occurs when the user clicks on the logout URL.  In this case /logout.  I receve a generic server error in the browser and the error_log shows "Premature end of script headers: app_dev.php".  If I hit refresh on the error page it goes back to my home page and I am logged out successfully.</p>
  
  <p>Here is my firewall section in security.yml:</p>
  
  <pre><code>firewalls:
      main:
          pattern: ^/
          form_login:
              provider: fos_userbundle
              check_path: fos_user_security_check
              csrf_provider: form.csrf_provider
          logout: true
          anonymous: true
  </code></pre>
  
  <p>Here is the access_control section of security.yml:</p>
  
  <pre><code>access_control:
      - { path: ^/login$, role: IS_AUTHENTICATED_ANONYMOUSLY, requires_channel:https }
      - { path: ^/register, role: IS_AUTHENTICATED_ANONYMOUSLY }
      - { path: ^/logout, role: IS_AUTHENTICATED_ANONYMOUSLY }
      - { path: ^/resetting, role: IS_AUTHENTICATED_ANONYMOUSLY }
      - { path: ^/admin/, role: ROLE_ADMIN }
  </code></pre>
  
  <p>Here is the fos_user section in config.yml</p>
  
  <pre><code>fos_user:
      db_driver: orm 
      firewall_name: main
      user_class: Wielding\BassBundle\Entity\User
  </code></pre>
  
  <p>I am generating the logout url in my twig form with:</p>
  
  <pre><code>&lt;a href="{{ path('fos_user_security_logout') }}"&gt;logout&lt;/a&gt;
  </code></pre>
  
  <p>If I am not logged into the site and I go manually to the logout url I get redirected back to the default index page without any error.  If I am logged in and manually type in the logout url I get the server error.  I have tried so many variations of config changes I can't even list them here.  They all failed.</p>
  
  <p>I even tried to write my own logout by invalidating the session in the controller and that generates the same error.  </p>
  
  <p>My only clue so far is an entry in dev.log:</p>
  
  <pre><code>[2013-07-27 14:51:26] request.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\ContextErrorException: "Warning: SessionHandler::write(): Parent session handler is not open in /home/dev2/app/cache/dev/classes.php line 407" at /home/dev2/app/cache/dev/classes.php line 407 {"exception":"[object] (Symfony\\Component\\Debug\\Exception\\ContextErrorException: Warning: SessionHandler::write(): Parent session handler is not open in /home/dev2/app/cache/dev/classes.php line 407 at /home/dev2/app/cache/dev/classes.php:407)"} []
  </code></pre>
  
  <p>Searching on this initially indicated that this was not something to worry about but I am out of other ideas.  This is my final task in getting security working and its freaking me out.</p>
  
  <p>I will gladly provide any other information needed to help solve this really annoying problem.  Thanks in advance for any assistance.</p>