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

$dispatcher = new EventDispatcher();

// you can attach event subscribers, which allow a single object to subscribe 
// to many events at once
$dispatcher->addSubscriber(new class implements EventSubscriberInterface {
    public static function getSubscribedEvents()
    {
        // here we subscribe our class methods to listen to various events
        return [
            // when anything fires a "an.event.occurred" call "onEventOccurred"
            'an.event.occurred' => 'onEventOccurred',
            // an array of listeners subscribes multiple methods to one event
            'another.event.happened' => ['whenAnotherHappened', 'sendEmail'],
        ];
    }

    function onEventOccurred(Event $event) {
        // process $event
    }

    function whenAnotherHappened(Event $event) {
        // process $event
    }

    function sendEmail(Event $event) {
        // process $event
    }
});