API

The API that événement exposes is defined by the Evenement\EventEmitterInterface. The interface is useful if you want to define an interface that extends the emitter and implicitly defines certain events to be emitted, or if you want to type hint an EventEmitter to be passed to a method without coupling to the specific implementation.

on($event, callable $listener)

Allows you to subscribe to an event.

Example:

$emitter->on('user.created', function (User $user) use ($logger) {
    $logger->log(sprintf("User '%s' was created.", $user->getLogin()));
});

Since the listener can be any callable, you could also use an instance method instead of the anonymous function:

$loggerSubscriber = new LoggerSubscriber($logger);
$emitter->on('user.created', array($loggerSubscriber, 'onUserCreated'));

This has the benefit that listener does not even need to know that the emitter exists.

You can also accept more than one parameter for the listener:

$emitter->on('numbers_added', function ($result, $a, $b) {});

once($event, callable $listener)

Convenience method that adds a listener which is guaranteed to only be called once.

Example:

$conn->once('connected', function () use ($conn, $data) {
    $conn->send($data);
});

emit($event, array $arguments = [])

Emit an event, which will call all listeners.

Example:

$conn->emit('data', [$data]);

The second argument to emit is an array of listener arguments. This is how you specify more args:

$result = $a + $b;
$emitter->emit('numbers_added', [$result, $a, $b]);

listeners($event)

Allows you to inspect the listeners attached to an event. Particularly useful to check if there are any listeners at all.

Example:

$e = new \RuntimeException('Everything is broken!');
if (0 === count($emitter->listeners('error'))) {
    throw $e;
}

removeListener($event, callable $listener)

Remove a specific listener for a specific event.

removeAllListeners($event = null)

Remove all listeners for a specific event or all listeners all together. This is useful for long-running processes, where you want to remove listeners in order to allow them to get garbage collected.