Hello all. I have modifed the article from here on user authentication to include cookies so the user does not have to log in each visit of the site. The problem is, I can't figure out how to let them logout. Here is the source code of the two files.

auth.php (included in each file)
PHP Code:

$uid = isset($_COOKIE['uid']) ? $_COOKIE['uid'] : $_SESSION['uid'];
$pwd = isset($_COOKIE['pwd']) ? $_COOKIE['pwd'] : $_SESSION['pwd'];

$_SESSION['uid'] = $uid;
$_SESSION['pwd'] = $pwd;

$sql = "SELECT * FROM info WHERE charname = '$uid' AND pass = '$pwd'";
$result = mysql_query($sql);
        $r = mysql_fetch_array($result); 
        $pre = $r["premium"];

if (!$result) {
    echo "A database error occurred while checking your login details!";
    echo mainFooter();

PHP Code:
    setcookie ("uid", "", mktime(12,0,0,1, 1, 1990));
    setcookie ("pwd", "", mktime(12,0,0,1, 1, 1990));

    header("Location: http://www.eqsig.com");
After the logout file redirects me to the homepage, it shows i am still logged in.