drupal/core/vendor/symfony/event-dispatcher

EventDispatcher Component

The Symfony EventDispatcher component implements the Mediator pattern in a simple and effective way to make your projects truly extensible.

use Symfony\Component\EventDispatcher\EventDispatcher;
use Symfony\Component\EventDispatcher\Event;

$dispatcher = new EventDispatcher();

$dispatcher->addListener('event_name', function (Event $event) {
    // ...
});

$dispatcher->dispatch('event_name');

Resources

You can run the unit tests with the following command:

$ cd path/to/Symfony/Component/EventDispatcher/
$ composer install
$ phpunit