Laravel 5.x : register services via service provider

AppServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Foundation\AliasLoader;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }

    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        if( count($this->services()) )
        {
            foreach($this->services() as $class)
            {
                $this->app->register($class);
            }
        }

        foreach($this->aliases() as $alias => $facade)
        {
            AliasLoader::getInstance()->alias($alias, $facade);
        }

        if( env('APP_DEBUG') == true )
        {
            $this->app->register(\Barryvdh\Debugbar\ServiceProvider::class);
        }
    }

    protected function services()
    {
        return [
            \Intervention\Image\ImageServiceProvider::class,
            \Barryvdh\DomPDF\ServiceProvider::class,
        ];
    }

    protected function aliases()
    {
       return [
            'Debugbar' => \Barryvdh\Debugbar\Facade::class,
            'Image' => \Intervention\Image\Facades\Image::class,
            'PDF' => Barryvdh\DomPDF\Facade::class, 
       ];
    }

}