event dispatcher
By @Symfony
Provides tools that allow your application components to communicate with each other by dispatching events and listening to them
event manager
By @Doctrine
The Doctrine Event Manager is a library that provides a simple event system.
event dispatcher contracts
By @Symfony
A set of event dispatcher abstractions extracted out of the Symfony components
zend eventmanager
By @Zend Framework
Implement event systems, signal slots, intercepting filters, and observers.