messenger_v1.php

<?php

// Message
class MyMessage
{
  // boring stuff that you should adapt to your fit.
  public $id = 42;
}

// Handler
use Symfony\Component\Messenger\Handler\MessageHandlerInterface;

// We should implements `MessageHandlerInterface` to register our handler
class MyMessageHandler implements MessageHandlerInterface
{
    // Thanks to the type hint Symfony will match the message with the good handler
    public function __invoke(MyMessage $message)
    {
        dump('We are in '.__CLASS__.' in method: '.__FUNCTION__, $message);

        // return emojis for the fun.
        return ['😍', '🎉', '🔥'];
    }
}

// Controller
class HelloController extends AbstractController
{
    #[Route('/hello', name: 'app_hello')]
    public function hello(MessageBusInterface $bus): Response
    {
        // dispatch the message
        $bus->dispatch(new MyMessage());

        return $this->render('hello/index.html.twig', [
            'value' => 'Hello',
        ]);
    }
}