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);
 }