title: share authentication between domain and subdomain in symfony 2.1
body: <p>In an application I implemented an javascript chat with long polling. Since there is just one Ajax Request per domain allowed I wanted to move the poll request to a subdomain.</p>
  
  <p>So I have two domains:</p>
  
  <pre><code>dev.site.com
  poll.dev.site.com
  </code></pre>
  
  <p>In my <code>config.yml</code> I entered the following:</p>
  
  <pre><code>framework:
      session:
          domain: .dev.site.com
          cookie_domain: .dev.site.com
  </code></pre>
  
  <p>But Symfony does not keep me logged in if I try to poll on the sub-domain via Ajax.</p>
  
  <p>Any idea on how to keep the session on the sub-domains?
  I'm using the FOSUserBundle</p>