$worker->onMessage = function($connection, $buffer)
{

    if (!isset($_SERVER)) {

        Http::header('WWW-Authenticate: Basic realm="My Realm"');
        Http::header('HTTP/1.0 407 Unauthorized');
        echo 'Text to send if user hits Cancel button';
        exit;
    } else {
        echo "<p>Hello {$_SERVER}.</p>";
        echo "<p>You entered {$_SERVER} as your password.</p>";
    }

};