yii2上传文件失败

<form action="<?= Url::to(['default/datafile']) ?>" method="post" enctype="multipart/form-data">
    <label for="file">Filename:</label>
    <input type="file" name="myFile" id="file" />
    <br />
    <input type="submit" name="submit" value="Submit" />
</form>

 public function actionDatafile(){
        if(empty($_FILES)){
            $status = 1;
            $info = '没有文件上传';
        }
        if($_FILES['myFile']['error'] === 0 || $_FILES['myFile']['error'] === '0' ){
            //文件上传成功
            $tmp = pathinfo($_FILES['myFile']['name']);
            $new_fname = $tmp['filename'].'_'.rand(1000000,9999999).'.'.$tmp['extension'];
            echo $new_fname;
            if(!move_uploaded_file($_FILES['myFile']['tmp_name'], '../runtime/file/'.$new_fname)){
                $status = 1;
                $info = '上传（移动）失败';
            }else{
                $status = 0;
                $info = '上传成功';
            }
        } else {
            //文件上传失败
            $info = '文件上传失败';
            switch($_FILES['myFile']['error']){
                case 1:
                    $info = '上传文件超过php.ini中upload_max_filesize配置参数';
                    break;
                case 2:
                    $info = '上传文件超过表单MAX_FILE_SIZE选项指定的值';
                    break;
                case 3:
                    $info = '文件只有部份被上传';
                    break;
                case 4:
                    $info = '没有文件被上传';
                    break;
                case 5:
                    $info = '上传文件大小为0';
                    break;
            }
            $status = 1;
        }
        return $info;
    }

public function beforeAction($action)
    {
        if ($action->id == 'datafile') {
            $this->enableCsrfValidation = false;
        }
 
        return parent::beforeAction($action);
    }