找不到类 - OOP

i'm watching a tutorials about CMS with OOP - PHP

i have error but to check it

i have to check ArticlesCatsModel.php first

on control page : (ArticlesCatsModel.php)

class ArticlesCatsModel
{

    public function Get($extra='')
    {
        $cats = array();
        System::Get('db')->Execute("SELECT * FROM `articles_cats` {$extra}");
        if(System::Get('db')->AffectedRows()>0)
            $cats = System::Get('db')->GetRows();


        return $cats;
    }
}
$m = new ArticlesCatsModel();
$m->Get();

?>  

when i run it i get error

Fatal error: Class 'System' not found in /var/www/html/cms/includes/models/ArticlesCatsModel.php on line 11

globals.php

<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);

define('ROOT', dirname(__FILE__));
define('INC', ROOT.'/includes/');
define('CORE', INC.'/core/');
define('MODELS', INC.'/models/');
define('CONTROLLERS', INC.'/controllers/');
define('LIBS', INC.'/libs/');


/**
 * Core Files
 */
require_once(CORE.'config.php');

require_once(CORE.'mysql.class.php');

require_once(CORE.'raintpl.class.php');

require_once(CORE.'system.php');

System::Store('db', new mysql());
System::Store('tpl', new RainTPL());
?>

Require the globals.php in your ArticlesCatsModel.php. So the System class can be used.

require_once('path/to/globals.php');

class ArticlesCatsModel
{

   public function Get($extra='')
   {
      $cats = array();
      System::Get('db')->Execute("SELECT * FROM `articles_cats` {$extra}");
      if(System::Get('db')->AffectedRows()>0)
         $cats = System::Get('db')->GetRows();


      return $cats;
   }
}

// why the lines below in the same file?
$m = new ArticlesCatsModel();
$m->Get();  

I think class ArticlesCatsModel could not find globals.php

Make sure globals.php is included when ArticlesCatsModel class is called