yii2视图找不到包

I have create a action on the Controller:

public function actionReports(){

        return $this->render('reports', []);
    }

And I have the following view 'reports':

<?
use frontend\models\ReportsActiveRecord;
use yii\data\ActiveDataProvider;
use yii\grid\GridView;
?>

<div>    


    <?php
    $dataProvider = new ActiveDataProvider([
        'query' => ReportsActiveRecord::find(),
        'pagination' => [
            'pageSize' => 5,
        ],
    ]);
    echo GridView::widget([
        'dataProvider' => $dataProvider,
    ]);    
    ?>
</div>

I am on the frontend of the advanced-app and I getting this error:

PHP Fatal Error – yii\base\ErrorException Class 'GridView' not found

I don't know why or I am missing something here?

Thanks

on your first line <? should be <?php