Wrench uses a single-process server, without threads, and blocks while processing data from any client. This means it has little hope of scaling in production.
You might like to use some middleware between your PHP application code and WebSocket clients in production. For example, you might use something like RabbitMQ’s STOMP + WebSockets Plugin. In any case, if you’re hoping to serve large numbers of clients, you should probably look into one of the evented IO based servers.