如何在Mozilla中找到Windows域名？

We have a Windows Domain Controller in the network which should be used for authentication,and in web application(wrotten by PHP) I want to find username and domain name,I use the following code,it works correctly in IE and Chrome but in Mozilla FireFox it does not find domain,How can I fix this problem?

<?PHP
$headers = apache_request_headers();

if (!isset($headers['Authorization'])){
    header('HTTP/1.1 401 Unauthorized');
    header('WWW-Authenticate: NTLM');
    exit;

}

$auth = $headers['Authorization'];

if (substr($auth,0,5) == 'NTLM ') {
    $msg = base64_decode(substr($auth, 5));
    if (substr($msg, 0, 8) != "NTLMSSP\x00")
        die('error header not recognised');

    if ($msg[8] == "\x01") {
        $msg2 = "NTLMSSP\x00\x02"."\x00\x00\x00\x00". // target name len/alloc
            "\x00\x00\x00\x00". // target name offset
            "\x01\x02\x81\x01". // flags
            "\x00\x00\x00\x00\x00\x00\x00\x00". // challenge
            "\x00\x00\x00\x00\x00\x00\x00\x00". // context
            "\x00\x00\x00\x00\x30\x00\x00\x00"; // target info len/alloc/offset

        header('HTTP/1.1 401 Unauthorized');
        header('WWW-Authenticate: NTLM '.trim(base64_encode($msg2)));
        exit;
    }
    else if ($msg[8] == "\x03") {
        function get_msg_str($msg, $start, $unicode = true) {
            $len = (ord($msg[$start+1]) * 256) + ord($msg[$start]);
            $off = (ord($msg[$start+5]) * 256) + ord($msg[$start+4]);
            if ($unicode)
                return str_replace("\0", '', substr($msg, $off, $len));
            else
                return substr($msg, $off, $len);
        }
        $user = get_msg_str($msg, 36);
        $domain = get_msg_str($msg, 28);
        $workstation = get_msg_str($msg, 44);


        print "You are $user from $workstation.$domain<BR>";
    }
}
?>