When I want to remove a Cookie I try
unset($_COOKIE[\'hello\']);
I see in my cookie browser from firefox that the cookie still exists. How
I had the same problem in my code and found that it was a cookie path issue. Check out this stack overflow post: Can't delete php set cookie
I had set the cookie using a path value of "/", but didn't have any path value when I tried to clear it, so it didn't clear. So here is an example of what worked:
Setting the cookie:
$cookiePath = "/";
$cookieExpire = time()+(60*60*24);//one day -> seconds*minutes*hours
setcookie("CookieName",$cookieValue,$cookieExpire,$cookiePath);
Clearing the cookie:
setcookie("cookieName","", time()-3600, $cookiePath);
unset ($_COOKIE['cookieName']);
Hope that helps.