// 结果
object(yii\web\UploadedFile)#223 (5) {
  ["name"]=>
  string(22) "蘑菇头跳舞啦.mp4"
  ["tempName"]=>
  string(14) "/tmp/phpshHSiG"
  ["type"]=>
  string(9) "video/mp4"
  ["size"]=>
  int(1224988)
  ["error"]=>
  int(0)
}

打印

public function actionCreate()
{
    $model = new Unit();
    $picurl = UploadedFile::getInstance($model, 'pic');
    echo '<pre>';
    var_dump($picurl);die;

    if ($model->load(Yii::$app->request->post()) && $model->save()) {
//            return $this->redirect(['view', 'id' => $model->id]);
        $this->doLog('创建单位', '单位ID' . $model->id);
        return $this->redirect(['index']);
    } else {
        return $this->render('create', [
            'model' => $model,
        ]);
    }
}

模型

['pic', 'file', 'checkExtensionByMimeType' => false, 'extensions' => 'mp4, flv', 'skipOnEmpty' => false],

视图

<?= $form->field($model, 'pic')->fileInput() ?>

没有发现错误啊

$pathName->saveAs($dirPath,true);
$model->path = $dirPathDb."/". $fileName;