title: How to detect session timeout in Symfony
body: <p>I'm currently working on a project with the PHP framework Symfony.
  I've configured secured pages, defined 30 minutes for the session timeout and set the page where the user should be redirect if an unauthenticated user tries to access a secured page.</p>
  
  <p>I've remarked that the user is also redirected there if the user tries to access a secured page after the user's session has expired.
  In this case, I would like to display a message basically saying that "Your session has expired. Please reconnect."</p>
  
  <p>How could I achieve this?</p>