错误提示：

php<?php
if (!defined('BASEPATH')) exit('No direct script access allowed');
class Article extends CI_Controller {
    public function __construct() {
        parent::__construct();
       
        $this->load->model('article_model', 'post');
    }
   
    public function index(){

        $this->load->view('admin/post_list.html');
    }
   
    public function add(){
        $this->load->model('category_model', 'cate');
        $data['category'] = $this->cate->fetch();
       
        $this->load->helper('form');
        $this->load->view('admin/post_add.html', $data);
    }
   
    public function save(){
        $this->load->library('form_validation', 'verify');
        $status = $this->verify->run('article');
       
        if ($status) {
            $data = array(
                'title' => $this->input->post('title'),
                'cid' => $this->input->post('category'),
                'date' => $this->input->post('date'),
                'keyword' => $this->input->post('keyword'),
                'description' => $this->input->post('description'),
                'excerpt' => $this->input->post('excerpt'),
                'thumbnail' => $this->input->post('thumbnail'),
                'password' => $this->input->post('password'),
                'content' => $this->input->post('content')
            );
           
            $this->post->add($data);
           
            success('admin/article', '添加文章成功');
        } else {
            $this->load->helper('form');
            $this->load->view('admin/post_add.html');
        }
    }
}
?>

为什么

php$this->load->library('form_validation', 'verify'); 
$this->load->model('category_model', 'cate');

这两个会加载失败？