FrankenPHP comes with a built-in Mercure hub! Mercure allows to push event in real-time to all the connected devices: they will receive instantly a JavaScript event.
No JS library or SDK required!
To enable the Mercure hub, update the Caddyfile as described on Mercure's website.
To push Mercure updates from your code, we recommend the Symfony Mercure Component (you don't need the Symfony full stack framework to use it).