nineskeletor/src/Controller/PublishController.php

<?php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Mercure\HubInterface;
use Symfony\Component\Mercure\Update;

class PublishController extends AbstractController
{
    public function sample($id){
        return $this->render('Home/publishsample.html.twig',[
            'id'=>$id
        ]);
    }

    public function publish($channel, $id, Request $request, HubInterface $hub): Response
    {
        $ret=$request->get("msg");
        $ret["from"]=[];
        $ret["from"]["id"]=$this->getUser()->getId();
        $ret["from"]["username"]=$this->getUser()->getUsername();
        $ret["from"]["displayname"]=$this->getUser()->getDisplayname();
        $ret["from"]["avatar"]=$this->generateUrl('app_minio_image',["file"=>"avatar/".$this->getUser()->getAvatar()]);


        $update = new Update(
            $channel."-".$id,
            json_encode(
                ['ret' => $ret])
        );

        $hub->publish($update);

        return new Response('published!');
    }
}