继承smarty类时遇到的有关问题，求指导！

left_delimiter="";
?>

assign("title",$title);
    $tpl->assign("content",$content);
    $tpl->display("default/test.tpl");
?>

       Smarty();
            $this->template_dir="./templates/";
            $this->compile_dir="./templates_c/";
            $this->config_dir="./configs/";
            $this->cache_dir="./cache/";
            $this->caching=true;
            $this->left_delimiter="";
            $this->assign('app_name','mySmartyTest');
        }
    }
       ?>

assign("title",$title);
    $tpl->assign("content",$content);
    $tpl->display("default/test.tpl");
?>