PHP检测用户是否是页面的粉丝并不总是有效

I'm using the following code as part of my facebook application that get user's permissions (mainly : likes ). This code will detect if the user is a fan of a page or not and based on that it will show some content or redirect him to another page, if he is not a fan. The main problem is that it works only one time or two times and then it shows nothing.

http://pastebin.com/RxefpmzD

<?php
    require 'lib/facebook.php';
    $facebook = new Facebook(array(
        'appId' => 'XXXXXXXXXXXXXXXXXX',
        'secret' => 'XXXXXXXXXXXXXXXXXXXXXXXXXX',
    ));

    $user = $facebook->getUser();

    if ($user) {
        try {
            $likes = $facebook->api("/me/likes/333605930105938");
            if( !empty($likes['data']) )
                echo "<iframe width=\"745\" height=\"535\" src=\"http://www.youtube.com/embed/".$donnees['link']."?fs=1&autoplay=1&loop=1\" frameborder=\"0\" allowFullScreen=\"\"></iframe>";
            else
                echo "<iframe width=\"745\" height=\"535\" src=\"scren.php?id=".$donnees['id']."\" frameborder=\"0\" allowFullScreen=\"\"></iframe>";
        } catch (FacebookApiException $e) {
            error_log($e);
            $user = null;
        }
    }
    if ($user) {
        $logoutUrl = $facebook->getLogoutUrl();
    } else {
        $loginUrl = $facebook->getLoginUrl(array(
            'scope' => 'user_likes'
        ));
    }
?>