I have tested this on my development computer, but now I have uploaded everything to the production server and I cant read out the value of the cookie.

I think the problem lies in the Serialization and Unserialization.

if (isset($_COOKIE['watched_ads'])){
    $expir = time()+1728000; //20 days
    $ad_arr = unserialize($_COOKIE['watched_ads']); // HERE IS THE PROBLEM
    $arr_elem = count($ad_arr);
    if (in_array($ad_id, $ad_arr) == FALSE){
        if ($arr_elem>10){
        array_shift($ad_arr);
        }
        $ad_arr[]=$ad_id;
        setcookie('watched_ads', serialize($ad_arr), $expir, '/');
    }
}

When I echo this: count($ad_arr) I receive the expected nr, 1 in this case, so there is a value there. But when I echo the value: echo $ad_arr[0]; I get nothing. Completely blank. No text at all.

Anybody have a clue?

if you need more info about something let me know...