Facebook iFrame App. getSession -login- problem

Question

Hello people.

I have a problem on FB iFrame app;

My php code is below

$session = $facebook->getSession();

if ($session) {
    $params = array('access_token' => $session['access_token']);
    try {
        $uid = $facebook->getUser();
        $me  = $facebook->api('/me', $params);
    } catch (FacebookApiException $e) {
        error_log($e);
    }
}
if (!empty($me)){
   #logged
}else{
   #redirect login url
}

I can login a page and i click a link (the link contains all of the $_GET data) but it redirect me my login page and i try to comminicate with facebook on login page, it was succesful.

So i logged in but this code can not see my login information and redirect me login page.