$fb = new ThinFacebookClient(
    CONFIG::FACEBOOK_APP_ID, 
    CONFIG::FACEBOOK_APP_SECRET, 
    CONFIG::FACEBOOK_APP_URL, 
    CONFIG::CANVAS_URL, 
    CONFIG::CANVAS_DOMAIN
  );
  if (!$fb->isAuthorized()) {
    $fb->redirectAuthorize($_GET);
  }

  $old_get_request = $fb->getAuthPassback();
  if (!empty($old_get_request)) {
    foreach($old_get_request as $key => $value) {
      $_GET[$key] = $value;
    }
  }

  $fb_user = $fb->getUserInfo($fbuid);