README

Part of the Jardis Business Platform — Enterprise-grade PHP components for Domain-Driven Design

Domain Events as first-class citizens. A lightweight PSR-14 event dispatcher — built for DDD applications where events drive the communication between layers and contexts. No framework, no overhead, no magic. Just what you need.

Why this Dispatcher?

Four classes, zero magic — EventDispatcher, ListenerProvider, Event, EventCollector
Priority ordering — listeners with higher priority are called first
Type-hierarchy matching — a listener on an interface catches all implementing events
Stoppable events — break the listener chain when an event is considered handled
EventCollector — collect events in the domain layer, dispatch them all at once in the application layer
PSR-14 compliant — works with any PSR-14 compatible code
100% test coverage — no mocks, real execution only

Installation

composer require jardisadapter/eventdispatcher

Quick Start

Define an Event

use JardisAdapter\EventDispatcher\Event;

final class OrderCreated extends Event
{
    public function __construct(
        public readonly string $orderId,
    ) {
    }
}

Register Listeners and Dispatch

use JardisAdapter\EventDispatcher\EventDispatcher;
use JardisAdapter\EventDispatcher\ListenerProvider;

$provider = new ListenerProvider();
$provider->listen(OrderCreated::class, function (OrderCreated $event): void {
    echo "Order {$event->orderId} created!";
});

$dispatcher = new EventDispatcher($provider);
$dispatcher->dispatch(new OrderCreated('ORD-42'));

Listener Registration

Priority-based Registration

$provider->listen(OrderCreated::class, $sendConfirmation, priority: 10);   // first
$provider->listen(OrderCreated::class, $updateInventory, priority: 5);     // second
$provider->listen(OrderCreated::class, $logEvent);                        // last (0)

Higher number = higher priority = called first.

Remove a Listener

$provider->remove(OrderCreated::class, $sendConfirmation);

Type-Hierarchy Matching (Wildcard)

A listener on an interface or parent class catches all events that implement or extend it:

interface PaymentEventInterface {}

final class PaymentReceived extends Event implements PaymentEventInterface {}
final class PaymentFailed extends Event implements PaymentEventInterface {}

// Catches both PaymentReceived AND PaymentFailed
$provider->listen(PaymentEventInterface::class, $paymentAuditor);

// Catches EVERY event that extends Event
$provider->listen(Event::class, $globalLogger);

Direct and wildcard listeners are sorted together by priority.

Stoppable Events

A listener can stop further processing:

$provider->listen(OrderCreated::class, function (OrderCreated $event): void {
    if ($event->orderId === 'BLOCKED') {
        $event->stopPropagation();  // no further listeners will be called
    }
}, priority: 100);

$provider->listen(OrderCreated::class, function (OrderCreated $event): void {
    // Only called if stopPropagation() was NOT invoked
});

Any event extending Event or implementing StoppableEventInterface supports this automatically.

EventCollector — Deferred Dispatch

Collect events in the domain layer, dispatch them later in the application layer:

use JardisAdapter\EventDispatcher\EventCollector;

$collector = new EventCollector();

// In the domain layer — record events
$collector->record(new OrderCreated($orderId));
$collector->record(new InventoryReserved($itemId));

// In the application layer — after the use case completes
$collector->dispatchAll($dispatcher);  // dispatches all, clears the list

The collector separates the occurrence of an event (domain) from its distribution (application). Ideal for use cases that produce multiple events.

$collector->count();     // number of collected events
$collector->events();    // read events without dispatching
$collector->clear();     // clear the list without dispatching

Error Handling

Situation	Behavior
Listener throws an exception	Propagates unchanged to the caller
No listener registered	Event is silently ignored
Event already stopped	No listener is called

No custom exception classes. Errors come from the listeners, not from the dispatcher.

Architecture

EventDispatcher (implements EventDispatcherInterface)
  │
  │  dispatch(object $event): object
  │  └── iterates listeners, respects StoppableEventInterface
  │
  └── ListenerProvider (implements ListenerProviderInterface, EventListenerRegistryInterface)
        │
        ├── listen()    register listener with priority
        ├── remove()    remove a listener
        └── getListenersForEvent()
              └── type-hierarchy matching + priority sorting

Event (abstract, implements StoppableEventInterface)
  └── stopPropagation() / isPropagationStopped()

EventCollector
  └── record() → dispatchAll() / events() / clear() / count()

The dispatcher is the postman — it receives the event and delivers it to all recipients. The listener provider is the address book. The event collector is the mailbox in the domain layer.

DDD Layer Rules

Layer	Responsibility
Domain	Defines event classes. Does not dispatch — returns events instead
Application	Receives `EventDispatcherInterface` via injection. Dispatches after use case execution
Infrastructure	Registers listeners in the `ListenerProvider`

Jardis Foundation Integration

In a Jardis DDD project, the dispatcher is wired into the DomainKernel via DomainApp::eventDispatcher():

// Inside a BoundedContext
$dispatcher = $this->resource()->eventDispatcher();

if ($dispatcher !== null) {
    $dispatcher->dispatch(new OrderCreated($orderId));
}

Three-State Semantics

Return value	Meaning
`EventDispatcher`	Dispatcher active, shared via ServiceRegistry
`null`	Package not installed — falls back to SharedRegistry
`false`	Event dispatching explicitly disabled

Development

cp .env.example .env    # Once
make install             # Install dependencies
make phpunit             # Run tests
make phpstan             # Static analysis (level 8)
make phpcs               # Coding standards (PSR-12)

Documentation

Full documentation, guides, and API reference:

docs.jardis.io/en/adapter/eventdispatcher

License

MIT License — free for any use, including commercial.

KI-gestützte Entwicklung

Dieses Package liefert einen Skill für Claude Code, Cursor, Continue und Aider mit. Installation im Konsumentenprojekt:

composer require --dev jardis/dev-skills

Mehr Details: https://docs.jardis.io/skills

jardisadapter / eventdispatcher

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