php - yii2怎么连接数据库操作

model文件

<?php

namespace app\models;

use Yii;
use yii\base\Model;
use yii\db\ActiveRecord;


class Folder extends \yii\db\ActiveRecord
{
    /**
     * @inheritdoc
     */
    public static function tableName()
    {
        return 'Folder';
    }

    public function search()
    {
        $query = Folder::find();
        $folders = $query->where(['pid' => 0,'type'=>0])->all();
        return $folders;
    }
}

controller文件：

<?php

namespace app\controllers;

use Yii;
use app\controllers\CommonController;
use app\models\LoginForm;
use app\models\home\Folder;

class HomeController extends CommonController
{

    public function actionIndex()
    {
        $model = new Folder();
        $folders = $model->search();
        return $this->render('index',[
                'folders' => $folders,
            ]);
    }
}

出现错误：
Unknown Class – yiibaseUnknownClassException
Unable to find 'appmodelshomeFolder' in file: /var/www/html/CodeNote/models/home/Folder.php. Namespace missing?
怎么处理？？？