title: How to persist signed_request with PHP SDK when user is not logged in?
body: <p>I have an app tab which does not require the user to authorize the app. When the tab first loads, I have access to the signed request like so: <code>$signed_request = $facebook-&gt;getSignedRequest();</code></p>
  
  <p>The app then makes various AJAX calls to the server. With each AJAX call, signed_request is not persisted. I would like the signed_request to be available during these AJAX calls so I can do <code>$signed_request = $facebook-&gt;getSignedRequest();</code> again.</p>
  
  <p>I have read that when a user is logged in, the JS SDK and PHP SDK share the signed_request via a cookie. Is there a cookie I can set during the initial page load that will persist signed_request during AJAX calls, so it is accessible through the PHP SDK?</p>