Kesalahan fatal: Kelas 'Illuminate\Database\Capsule\Manager' tidak ditemukan

saya punya file kelas database.php:

<?php
use Illuminate\Database\Capsule\Manager as Capsule;

$capsule = new Capsule;

$capsule->addConnection([
 'driver'     => $app->config->get('db.driver'),
 'host'       => $app->config->get('db.host'),
 'database'   => $app->config->get('db.name'),
 'username'   => $app->config->get('db.username'),
 'password'   => $app->config->get('db.password'),
 'charset'    => $app->config->get('db.charset'),
 'collation'  => $app->config->get('db.collation'),
 'prefix'     => $app->config->get('db.prefix')
]);

$capsule->bootEloquent();

namun itu memunculkan kesalahan ini:

Kesalahan fatal: Kelas 'Illuminate\Database\Capsule\Manager' tidak ditemukan di C:\xampp\htdocs\boilerplate\app\database.php on line 4

saya telah membutuhkannya di start.php

<?php
require 'database.php';
//############ NAMESPACING ################//
use Slim\Slim; //import slim
use Noodlehaus\Config;
use Boilerplate\User\User;
//#########################################//

session_cache_limiter(false);
session_start();

ini_set('display_errors','on'); //TURN OFF ON LIVE SITE

define('INC_ROOT', dirname(__DIR__)); //create local root

require INC_ROOT . '/vendor/autoload.php'; // autoload in all the      dependencies in the vendor files.

$app = new Slim([
'mode' => file_get_contents(INC_ROOT . '/mode.php')
]); //assign the entire app file to a variable

$app->configureMode($app->config('mode'), function() use ($app){
$app->config = Config::load(INC_ROOT . "/app/config/{$app->mode}.php"); //pull in the config file
});

$app->container->set('user', function(){
    return new User;
});