Cookie checking and loggin out

[Defender1]

Would this be an effective way to delete a cookie, then refresh the page so it displays the correct message? (displays logged in if cookie exists, not logged in if it doesn't)

$is_set = $HTTP_COOKIE_VARS['cookie_name'];

if($is_set != "") // $is_set has a value, so cookie exists/
{
    setcookie("3dartisan_username", "", time() - 100);
    setcookie("3dartisan_password", "", time() - 100);
    header("Location: $PHP_SELF"); // refresh the page to display correct message
}