title: Something like a callback delegate function in php
body: <p>I would like to implement something similar to a c# delegate method in PHP.  A quick word to explain what I'm trying to do overall:  I am trying to implement some asynchronous functionality. Basically, some resource-intensive calls that get queued, cached and dispatched when the underlying system gets around to it. When the asynchronous call finally receives a response I would like a callback event to be raised.</p>
  
  <p>I am having some problems coming up with a mechanism to do callbacks in PHP.  I have come up with a method that works for now but I am unhappy with it.  Basically, it involves passing a reference to the object and the name of the method on it that will serve as the callback (taking the response as an argument) and then use eval to call the method when need be.  This is sub-optimal for a variety of reasons, is there a better way of doing this that anyone knows of? </p>