MagentoServiceProvider.php

<?php
namespace App\Providers;

use Illuminate\Support\ServiceProvider;

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

    /**
     * Register services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->bind('Magento', function () {
            require_once '../../path-to-your-magento-installation/app/Mage.php';

            return \Mage::app();
        });
    }
}