$id=$row['id'];
$password=$row['password'];
$time=md5(time().$password);
$userid=$id.":".$time;

setcookie("userid",$userid,time() +3600*24*120);
list($id_user,$hash) = explode(':',$_COOKIE['userid']);
mysql_query("UPDATE users SET cookie='$hash' WHERE id='$id'",$connect) or die(mysql_error());
header("Location: index.php");