Phalcon\Mvc\Dispatcher\Exception: SourcesController handler class cannot be loaded

<?php
 
error_reporting(E_ALL);
ini_set('display_errors', 1);
 
$debug = new \Phalcon\Debug();
$debug->listen();
  $dir = '/usr/share/nginx/html/admin/';
    /**
     * Read the configuration
     */
    $config = include $dir . "app/config/config.php";
 
    /**
     * Read auto-loader
     */
    include $dir . "app/config/loader.php";
 
    /**
     * Read services
     */
    include $dir . "app/config/services.php";
 
    /**
     * Handle the request
     */
    $application = new \Phalcon\Mvc\Application($di);
 
    echo $application->handle()->getContent();