symfony/symfony — pull request #4840 by Marlinc (2012-07-10 15:28:33+00:00)
Title: [EventDispatcher] Event on first listener added

The EventDispatcher will now dispatch a event if the first listener was added.
And thus letting the other code that something wants to know if a event happend.

This could be usage full in many cases.
The thing I find it usefull for the POSIX signals in PHP.
This way I can listen for a signal only if somewere in the code something wants to listen to it.
That way PHP won't listen for a signal if not necessary.