getSignedRequest() always comes back NULL
===

Were building an app on a facebook page (currently in Developement, can't show it.) and we've hit a problem.

We are trying to get the language the user set his Facebook (fr_CA, en_US, etc.)

So we are going via the getSignedRequest() function.

    $facebook = new Facebook(array(
      'appId'  => 'xxxxxxxxxxxxxx',
      'secret' => 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
    ));

    // Get User ID
    $request = $facebook->getSignedRequest();
    @list($language, $country, $test) = explode('_', $request['user']['locale']);

    var_dump($request);

We are using the PHP SDK, and yes, the facebook.php was included earlier in the page.

The vardump is always showing NULL. Why don't we get anything?