$router = new Router();
$router->addRoute('/user/[i:id]', function(\Nyholm\Psr7\Request $request){
    // work here with the request in PSR-7 way

    $psr17Factory = new \Nyholm\Psr7\Factory\Psr17Factory();

    $responseBody = $psr17Factory->createStream('Hello world');
    $response = $psr17Factory->createResponse(200)->withBody($responseBody);
    (new \Zend\HttpHandlerRunner\Emitter\SapiEmitter())->emit($response);
});

$router->registerMiddleware('/user/[i:id]', function(string $route, array $parameters){
    $psr17Factory = new \Nyholm\Psr7\Factory\Psr17Factory();

    $creator = new \Nyholm\Psr7Server\ServerRequestCreator(
        $psr17Factory, // ServerRequestFactory
        $psr17Factory, // UriFactory
        $psr17Factory, // UploadedFileFactory
        $psr17Factory  // StreamFactory
    );

    return $creator->fromGlobals();
});