A simple observer pattern implementation based on symfony event handler (PSR-14 compatible)

Subscribe and listen for various events that occur within your application.

Requirements

Make sure that your server is configured with following PHP version and extensions:

• PHP 8.0+
• Spiral framework 2.9+

Installation

You can install the package via composer:

composer require spiral-packages/event-bus

After package install you need to register bootloader from the package.

protected const LOAD = [
    // ...
    \Spiral\EventBus\Bootloader\EventBusBootloader::class,
];

or

namespace App\Bootloader;

use Spiral\EventBus\Bootloader\EventBusBootloader as BaseBootloader

class EventBusBootloader extends BaseBootloader
{
    protected const LISTENS = [
        \App\Event\UserCreated::class => [
            \App\Listener\SendWelcomeMessageListener::class
        ],
        //...
    ];
}

Usage

At first need create config file app/config/event-bus.php, where you can specify listeners.

<?php

declare(strict_types=1);

return [
    'queueConnection' => env('EVENT_BUS_QUEUE_CONNECTION'), // default queue connection for Listeners with \Spiral\EventBus\QueueableInterface
    'discoverListeners' => env('EVENT_BUS_DISCOVER_LISTENERS', true), // Discover listeners with \Spiral\EventBus\Attribute\Listener attribute
    'listeners' => [
        UserDeleted::class => [
            DeleteUserComments::class,
        ]
    ],
    'interceptors' => [
        BroadcastEventInterceptor::class
    ]
];

You can also register listeners via Spiral\EventBus\ListenerRegistryInterface

class MyPackageBootloader extends Spiral\Boot\Bootloader\Bootloader
{
    public function start(Spiral\EventBus\ListenerRegistryInterface $registry) 
    {
        $registry->addListener(UserDeleted::class, DeleteUserComments::class);
    }
}

Event example

class UserDeleted 
{
    public function __construct(public string $name) {}
}

Listener example

Make sure to use variable $event for event handler method. It's required.

class DeleteUserComments 
{
    public function __construct(private CommentService $service) {}
    
    public function __invoke(UserDeleted $event)
    {
        $this->service->deleteCommentsForUser($event->name);
    }
}

Listener example with attributes

If you are using listeners with attributes 'discoverListeners' = true, you don't need to register them, they will be registered automatically.

use Spiral\EventBus\Attribute\Listener;

class DeleteUserComments 
{
    public function __construct(private CommentService $service) {}
    
    #[Listener]
    public function handleDeletedUser(UserDeleted $event)
    {
        $this->service->deleteCommentsForUser($event->usernname);
    }
    
    #[Listener]
    public function handleCreatedUser(UserCreated $event)
    {
        $this->service->creaateUserProfile($event->usernname);
    }
    
    #[Listener]
    public function notifyAdmins(UserCreated|UserDeleted $event)
    {
        $this->service->notifyAdmins($event->usernname);
    }
}

Listener example that should be handled in a queue

If you want to push listener to a queue, you can add Spiral\EventBus\QueueableInterface

class DeleteUserComments implements \Spiral\EventBus\QueueableInterface
{
    // ...
}

Event dispatching

use Symfony\Component\EventDispatcher\EventDispatcherInterface;

class UserService 
{
    public function __construct(private EventDispatcherInterface $events) {}
    
    public function deleteUserById(string $id): void
    {
        $user = User::findById($id);
        //.. 
        
        $this->events->dispatch(
            new UserDeleted($user->username)
        );
    }
}

Interceptors

The package provides convenient Bootloader to configure core interceptors Spiral\EventBus\Bootloader\EventBusBootloader automatically:

namespace App\Bootloader;

use Spiral\EventBus\Bootloader\EventBusBootloader as BaseBootloader

class EventBusBootloader extends BaseBootloader
{
    protected const INTERCEPTORS = [
        \App\Event\Interceptor\BroadcastEventInterceptor::class,
        //...
    ];
}

or via config app/config/event-bus.php

<?php

declare(strict_types=1);

return [
    // ...
    'interceptors' => [
        BroadcastEventInterceptor::class
    ]
];

namespace App\Event\Interceptor;

use Spiral\Broadcasting\BroadcastInterface;

class BroadcastEventInterceptor implements \Spiral\Core\CoreInterceptorInterface
{
    public function __construct(
        private BroadcastInterface $broadcast
    ) {}
    
    public function process(string $eventName, string $action, array , CoreInterface $core): mixed
    {
        $event = $parameters['event']; // Event object
        $listeners = $parameters['listeners']; // array of invokable listeners
        
        $result = $core->callAction($eventName, $action, $parameters);     
        
        if ($event instanceof ShouldBroadcastInterface) {
            $this->broadcast->publish(
                $event->getBroadcasTopics(), 
                \json_encode($event->toBroadcast())
            );
        }
        
        return $result;
    }
}

Testing

composer test

If you are using spiral/testing package in your application, you can additionally use trait Spiral\EventBus\Testing\InteractsWithEvents in your tests cases.

class EventDispatcherTest extends TestCase
{
    use \Spiral\EventBus\Testing\InteractsWithEvents;

    public function testDispatchEvent(): void
    {
        $events = $this->fakeEventDispatcher();
    
        $this->getDispatcher()->dispatch(new SimpleEvent());
    
        $events->assertListening(SimpleEvent::class, SimpleListener::class);
        $events->assertListening(SimpleEvent::class, ListenerWithAttributes::class, 'methodA');
        
        $events->assertDispatched(SimpleEvent::class)
        
        $events->assertDispatched(SimpleEvent::class, function(SimpleEvent $event) {
            return $event->someProperty === 'foo';
        });

        $events->assertDispatchedTimes(SimpleEvent::class, 10);
        
        $events->assertNotDispatched(AnotherSimpleEvent::class);
        
        $events->assertNotDispatched(AnotherSimpleEvent::class);
        
        $events->assertNothingDispatched();
    }
}

Changelog

Please see CHANGELOG for more information on what has changed recently.

Contributing

Please see CONTRIBUTING for details.

Security Vulnerabilities

Please review our security policy on how to report security vulnerabilities.

Credits

• butschster
• All Contributors

License

The MIT License (MIT). Please see License File for more information.