James Morris has an interesting new post to his site about the creation of a real-time web service that could be used for iOS applications via Websockets. He chose Ratchet for the handling (a PHP-based websocket tool) combined with Redis and Silex.
I was approached by a betting/gambling development company who potentially needed a middleware building that would pull from an existing gambling web service and basically transmit to connected iPhone clients the changes from the web service. At first, the obvious answer might be to create another REST web service that the iPhone clients could just ping for changes. However, one of the devs explained that this wouldn't be fast enough, or scale - they'd need changes to be transmitted as soon as possible, as the app would be a real-time betting app and there'd be thousands of connections to the server.
His solution involved hooking together Ratchet, Redis, Silex and Predis-async to create this sample tool for handling the websocket requests. it uses the "pubsub" mechanism of Redis to push the updates out to listening clients.