初学者smarty配置出错，高手指教

刚学smarty,看着教程配置的，

<?php
 include_once 'smarty/Smarty.class.php';
 $smarty=new Smarty();
 $smarty->config_dir('smarty/Config_File.class.php');
 $smarty->caching=false;
 $smarty->template_dir="./templates";
 $smarty->compile_dir="./templates_c";
 $smarty->cache_dir="./smarty_cache";
 

 $smarty->left_delimiter="{";
 $smarty->right_delimiter="}";
?>


一调试，出现：Fatal error: Call to undefined method Smarty::config_dir() in D:\PHPnow-1.5.4\htdocs\News\smarty_inc.php on line 4

怎么回事？哪位高手指教一下?

提供一个比较适合新手的图文,,,
http://www.jianyu87.com/201010175.html