Add HTTP authentication code to PHP page

// Digest HTTP Authentication
// To enable, add user: "name" => "password".
//$users = array();
$users = array(""=>"");

// If auth is enabled:
if (!empty($users)) {
    if (empty($_SERVER['PHP_AUTH_DIGEST'])) {
        header('HTTP/1.1 401 Unauthorized');
        header('WWW-Authenticate: Digest realm="' . $realm . '",qop="auth",nonce="' . uniqid() . '",opaque="' . md5($realm) . '"');
        die("Bye-bye!n");
    }

    // Analyze the PHP_AUTH_DIGEST variable
    if (!($data = httpDigestParse($_SERVER['PHP_AUTH_DIGEST'])) || !isset($users[$data['username']])) {
        die("Wrong Credentials!n");
    }

    // Generate the valid response
    $A1 = md5($data['username'] . ':' . $realm . ':' . $users[$data['username']]);
    $A2 = md5($_SERVER['REQUEST_METHOD'] . ':' . $data['uri']);
    $valid_response = md5($A1 . ':' . $data['nonce'] . ':' . $data['nc'] . ':' . $data['cnonce'] . ':' . $data['qop'] . ':' . $A2);

    if ($data['response'] != $valid_response) {
        die("Wrong Credentials!n");
    }
    
    // ok, valid username & password
    $httpUsername = $data['username'];
}
function httpDigestParse($txt)
{
    // protect against missing data
    $needed_parts = array('nonce' => 1, 'nc' => 1, 'cnonce' => 1, 'qop' => 1, 'username' => 1, 'uri' => 1, 'response' => 1);
    $data = array();
    $keys = implode('|', array_keys($needed_parts));

    preg_match_all('@(' . $keys . ')=(?:(['"])([^2]+?)2|([^s,]+))@', $txt, $matches, PREG_SET_ORDER);

    foreach ($matches as $m) {
        $data[$m[1]] = $m[3] ? $m[3] : $m[4];
        unset($needed_parts[$m[1]]);
    }

    return $needed_parts ? false : $data;
}