How to trigger and listen to events with class-based methods in a cool way in CodeIgniter 4

events-codeigniter4.md

Defining Events

Create class event App\Events\TestEvent::class

<?php

namespace App\Events;

class TestEvent
{
    public string $hello;

    public function __construct(string $hello = null)
    {
        $this->hello = $hello;
    }
}

### Defining Listeners

Create class listener App\Listeners\TestListener::class with magic method __invoke()

<?php

namespace App\Listeners;

use App\Events\TestEvent;

class TestListener
{
    public function __construct(TestEvent $event)
    {
    }
 
    public function __invoke(TestEvent $evet)
    {
        log_message('error', $evet->hello);
    }
}

Dispatching Events

<?php

namespace App\Controllers;

use App\Controllers\BaseController;
use App\Events\TestEvent;
use CodeIgniter\Events\Events;

class ProfileController extends BaseController
{
    public function index()
    {
        Events::trigger(TestEvent::class, new TestEvent('world'));
    }

Add as many arguments as you want and pass them to the listener in __construct or __invoke

class ProfileController extends BaseController
{
    public function index()
    {
        Events::trigger(TestEvent::class, new TestEvent('world'), $arg1 = 'args1', $arg2 = 'arg2', $argN = 'argN');
    }
    
}

class TestListener
{
    public function __construct(TestEvent $event, $arg1 = 'args1', $arg2 = 'arg2', $argN = 'argN')
    {
    }
 
    public function __invoke(TestEvent $evet, $arg1, $arg2, $argN)
    {
        log_message('error', $evet->hello);
    }
}

Registering Events and Listeners

Create class App\Providers\EventServiceProvider

<?php

namespace App\Providers;

use CodeIgniter\Events\Events;

class EventServiceProvider
{
    /**
     * The event to listener mappings for the application.
     *
     * @var array<class-string, array<int, class-string>>
     */
    protected static $listen = [
        \App\Events\TestEvent::class => [
            \App\Listeners\TestListener::class,
        ]
    ];

    public static function register()
    {
        foreach (static::$listen as $event => $listeners) {
            foreach (array_unique($listeners, SORT_REGULAR) as $listener) {
                Events::on($event, static function (...$callable) use ($listener) {
                    (new $listener(...$callable))(...$callable);
                });
            }
        }
    }
}

Register App\Providers\EventServiceProvider

Finnaly you need to register App\Providers\EventServiceProvider in config events app\Config\Events.php see example bellow, and see the log

\App\Providers\EventServiceProvider::register();