php_laravel_laracasts/app/Providers/EventServiceProvider.php

<?php

namespace App\Providers;

use App\Listeners\QueryExecutedListener;
use Illuminate\Database\Events\QueryExecuted;
use Illuminate\Support\Facades\Event;
use Illuminate\Foundation\Support\Providers\EventServiceProvider as ServiceProvider;

class EventServiceProvider extends ServiceProvider
{
    /**
     * The event listener mappings for the application.
     *
     * @var array
     */
    protected $listen = [
        QueryExecuted::class => [
            QueryExecutedListener::class
        ],
    ];
}