Plugins: Handling Events

Labrador emits semantic, data-rich events throughout the processing of an application to ensure that you can respond to meaningful occurrences while being decoupled from the code doing the actual processing. The Labrador async-event library provides the functionality that emits events and allows you to attach listeners that respond to those events. This library allows for listeners to be processed in an async context and provides a wealth of functionality for working in async applications.

Implementing EventAwarePlugin

In our example we're going to log out a message each time Labrador emits an out-of-the-box event.


namespace Acme;

use Cspray\Labrador\AsyncEvent\Event;
use Cspray\Labrador\AsyncEvent\EventEmitter;
use Cspray\Labrador\Engine;
use Cspray\Labrador\Plugin\EventAwarePlugin;
use Psr\Log\LoggerInterface;

class EventLoggingPlugin implements EventAwarePlugin {

    private $listenerIds = [];
    private $logger;

    public function __construct(LoggerInterface $logger) {
        $this->logger = $logger;

    public function registerEventListeners(EventEmitter $emitter) : void {
        $this->listenerIds[] = $emitter->on(Engine::START_UP_EVENT, function(Event $event) {
            $this->logger->info(sprintf('We started up the Engine using %s', get_class($event->getTarget()))); 
        $this->listenerIds[] = $emitter->on(Engine::SHUT_DOWN_EVENT, function() {
            $this->logger->info('The Engine is shutting down.');

    public function removeEventListeners(EventEmitter $emitter) : void {
        foreach ($this->listenerIds as $listenerId) {


The EventAwarePlugin allows you to both register and remove listeners from the EventEmitter. Registering event listeners happens as a normal course of Plugin loading and will happen automatically upon executing Engine::run. To have listeners removed the Plugin must be explicitly removed from the Pluggable using Pluggable::removePlugin.

Next Steps

If you simply need to do something when your Plugin completes the loading process check out the Plugins: Booting Up documentation next.