index.php

$pipeline = new Pipeline([
    function ($request, $next) {
        if (!isset($request->getAttribute('user'))) {
            return new Response(401, 'Sai daqui demônio!');
        }

        return $next->handle($request);
    },

    function ($request, $next) {
        return new Response(200, 'Oi :D');
    }
]);

$request = Request::fromGlobals();

echo $pipeline->handle($request);