<?php Swoole\Server->getCallback(string $eventName)
The event callback that you want to retrieve using the event name, no need to include
on, just the name like
Request, this relates to the server callback events
If success, it returns the registered callback, otherwise it returns
Get the callback function bind on a server event.
When the callback event has been registered with the server, this method will return what was registered, so it will return the four different event registration callback types: Closure, string or an array. If the callback does not exist it will return