CMS with PHP- mkdir()

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

on control page : (articles.php)

<?php
require_once('globals.php');
require_once(CONTROLLERS.'ArticlesController.php');

$articlesmodel = new ArticlesModel() ; 

$catsmodel     = new ArticlesCatsModel();

$controller    = new ArticlesController($articlesmodel,$catsmodel);

$controller->show();

?>

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()); //class RainTPL
?>

ArticlesController.php

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


require_once(MODELS.'ArticlesModel.php');
require_once(MODELS.'ArticlesCatsModel.php');


class ArticlesController
{

    private $articlesModel; //Articles Model Object
    private $articlesCatsModel; //Articles Cat Model Object
                               //object of ArticlesModel class
    public function __construct(ArticlesModel $articlesmodel,ArticlesCatsModel $catsmodel)
    {

        $this->articlesModel     = $articlesmodel ;
        $this->articlesCatsModel = $catsmodel ; 
    }


    //add new cat
    public function Add()
    {



    }

    public function Show()
    {
        // array of articles from model :D 
        /*
           he takes object from Articlesmodel.php
           like private articles model 
           then he  call the Get function 
           from  ArticlesModel Class 
        */

        $articles = $this->articlesModel->Get();
        $cats     = $this->articlesCatsModel->Get();


        //put them inside the template after getting them
        System::Get('tpl')->assign('articles',$articles)    ;   
        System::Get('tpl')->assign('cats',$cats)    ;   

        // show them in the templatee

        System::Get('tpl')->draw('blog');
    }

}

The ArticlesCatsModel

ArticlesCatsModel includes/model

The ArticleModel The ArticleModel

While running articles.php

i get error

Warning: mkdir(): Permission denied in /var/www/html/cms/includes/core/raintpl.class.php on line 320

Fatal error: Uncaught exception 'RainTpl_NotFoundException' with message 'Template blog.html not found!' in /var/www/html/cms/includes/core/raintpl.class.php:270 Stack trace: #0 /var/www/html/cms/includes/core/raintpl.class.php(166): RainTPL->check_template('blog') #1 /var/www/html/cms/includes/controllers/ArticlesController.php(67): RainTPL->draw('blog.html') #2 /var/www/html/cms/articles.php(11): ArticlesController->Show() #3 {main} thrown in /var/www/html/cms/includes/core/raintpl.class.php on line 270