Symfony 7.4 EventDispatcher Component

GitHub: https://github.com/symfony/event-dispatcher Docs: https://symfony.com/doc/7.4/components/event_dispatcher.html

Quick Reference

Creating a Custom Event

use Symfony\Contracts\EventDispatcher\Event;

final class OrderPlacedEvent extends Event
{
    public function __construct(private Order $order) {}

    public function getOrder(): Order
    {
        return $this->order;
    }
}

Dispatching an Event

$event = new OrderPlacedEvent($order);
$dispatcher->dispatch($event);

Event Listener with #[AsEventListener] (Recommended)

use Symfony\Component\EventDispatcher\Attribute\AsEventListener;

#[AsEventListener]
final class OrderListener
{
    public function __invoke(OrderPlacedEvent $event): void
    {
        // handle event
    }
}

Multiple Listeners on One Class

use Symfony\Component\EventDispatcher\Attribute\AsEventListener;

final class MyMultiListener
{
    #[AsEventListener]
    public function onOrderPlaced(OrderPlacedEvent $event): void { /* ... */ }

    #[AsEventListener(event: 'foo', priority: 42)]
    public function onFoo(): void { /* ... */ }
}

Event Subscriber

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\KernelEvents;

class StoreSubscriber implements EventSubscriberInterface
{
    public static function getSubscribedEvents(): array
    {
        return [
            KernelEvents::RESPONSE => [
                ['onKernelResponsePre', 10],
                ['onKernelResponsePost', -10],
            ],
            OrderPlacedEvent::class => 'onPlacedOrder',
        ];
    }

    // ... handler methods
}

Stopping Event Propagation

public function onPlacedOrder(OrderPlacedEvent $event): void
{
    $event->stopPropagation();
}

Kernel Events

• kernel.request (KernelEvents::REQUEST)
• kernel.controller (KernelEvents::CONTROLLER)
• kernel.response (KernelEvents::RESPONSE)
• kernel.exception (KernelEvents::EXCEPTION)

Debugging

php bin/console debug:event-dispatcher
php bin/console debug:event-dispatcher kernel.exception

Full Documentation

For complete details including service container integration, event aliases, before/after filters, listener vs subscriber comparison, all kernel event types, priority system, and advanced patterns, see references/event-dispatcher.md.