Authenticate

Hvad er der galt her?

index.php:
<?
include('connect.php');
include('authenticate.php');


login_validate($PHP_AUTH_USER, $PHP_AUTH_PW);

?>

authenticate.php:
<?

function authenticate($user, $pass)
{
        header('WWW-Authenticate: Basic realm=""');
        header('HTTP/1.0 401 Unauthorized');
    exit;
}

function login_validate($user, $pass)
{
    $sql = "SELECT * FROM user WHERE name='$user' AND pass='$pass'";
    $result = mysql_query($sql);

    $row = mysql_fetch_array($result);
    $id = $row['user_id'];

        if($id)
                { }
        elseif (($user ==  '') or ($pass ==  ''))
                { authenticate($user, $pass); }
        else
                { authenticate($user, $pass); }

}
?>