title: Facebook PHP: After user logs out of facebook, they can't login to my app with another user
body: <p>Sorry for the confusing title, here's the situation...</p>
  
  <ol>
  <li>A user logs into my app with Facebook</li>
  <li>The user logs out of facebook....someone else comes to the computer...</li>
  <li>The second user tries to access my app (different facebook account, same computer)</li>
  <li>They can't...instead the script gets the access token for the previous user.</li>
  </ol>
  
  <p>I'm using the facebook PHP SDK.</p>
  
  <p>When the user tries to login for the first time I do the following;</p>
  
  <pre><code>unset($_REQUEST);
  unset($_COOKIE); //don't know if both are necessary
  session_destroy();
  </code></pre>
  
  <p>Yet SOMEHOW the new fb account is still recognized as the last one (I get the previously logged in users access token which throws an exception when I try to use it since that user isn't logged in anymore).</p>
  
  <p>Do I need to use the logout function? I assume that logs the user out of facebook, which isn't want I want to do, just start fresh with a new user in my app.</p>
  
  <p>Any ideas? I'm really at loss on where this data is persisting from since I'm clearing everything. Hopefully its something stupid I'm missing but I thought I'd ask in case anyone knew anything.</p>