User authentication + PHP + IIS

Zakaj ne morem delat z user authentication v PHPju na IIS??? Nonstop mi javlja neke errorje. PHP na IIS poganjam kot module (z php4isapi.dll) in ne kot CGI. Za začetek sem probal tole kodo: if (!isset($_SERVER['PHP_AUTH_USER'])) {
header("WWW-Authenticate: Basic realm="My Realm"");
header("HTTP/1.0 401 Unauthorized");
echo "Text to send if user hits Cancel buttonn";
exit;
} else {
echo "

Hello {$_SERVER['PHP_AUTH_USER']}.

";
echo "

You entered {$_SERVER['$PHP_AUTH_PW']} as your password.

";
}
?>
Koda je direktno iz manuala!

Warning: Cannot add header information - headers already sent by (output started at c:\inetpub\wwwroot\test.php:6) in c:\inetpub\wwwroot\test.php on line 8

Warning: Cannot add header information - headers already sent by (output started at c:\inetpub\wwwroot\test.php:6) in c:\inetpub\wwwroot\test.php on line 9