Authentication problem on

i have a php script that was working properly until my host upgraded php version to 4.2.3 ,
after that, script doesnt work;
i need assistance,

<?
// login window
function AuthMsg() {
GLOBAL $user, $pw,$auth,$PHP_AUTH_USER,$PHP_AUTH_PW;

header('WWW-Authenticate: Basic realm="Doðrulama Örneði"');
header('HTTP/1.0 401 Unauthorized');

?>
<HTML>
<HEAD>

</HEAD>

<BODY>

</BODY>
</HTML>
</HTML>
<?

exit;
}

function Authenticate() {
GLOBAL $PHP_AUTH_USER, $PHP_AUTH_PW, $user, $pw,$auth;

$auth=False;

if(!empty($PHP_AUTH_USER) && !empty($PHP_AUTH_PW)) {
if($PHP_AUTH_USER==$user && $PHP_AUTH_PW==$pw)
$auth=True;
}

if(!$auth) {
AuthMsg();
exit;
}
}
//-----------------------------------

$user="abc";
$pw ="123";

if(!isset($act)) $act="";

if($act=="logout") {
AuthMsg();
exit;
}

Authenticate();

echo "your pass <B>$PHP_AUTH_PW</B><BR>";
echo '<A HREF="'.$PHP_SELF.'?act=logout">Logout</A>';
include ("main.php");
?>

what did you upgrade from

4.2.3 has register_globals OFF by default... maybe your older version has it ON by default

i suspect that may be your porlbem after seeing

$PHP_AUTH_USER

instead of

$_SERVER['PHP_AUTH_USER'];