public function actionCreate()
{
  $model = new DynamicModel([
    'nama', 'file_id'
    ]);
  // behavior untuk upload file
  $model->attachBehavior('upload', [
    'class' => 'mdm\upload\UploadBehavior',
    'attribute' => 'file',
    'savedAttribute' => 'file_id' // coresponding with $model->file_id
  ]);
  // rule untuk model
  $model->addRule('nama', 'string')
    ->addRule('file', 'file', ['extensions' => 'jpg']);
  if ($model->load(Yii::$app->request->post()) && $model->validate()) {
    if ($model->saveUploadedFile() !== false) {
      Yii::$app->session->setFlash('success', 'Upload Sukses');
    }
  }
  return $this->render('upload',['model' => $model]);
}

<?php
use yii\helpers\Html;
use yii\widgets\ActiveForm;
/* @var $this yii\web\View */
?>
<div>
  <?php
  $form = ActiveForm::begin([
      'options' => [ 'enctype' => 'multipart/form-data']
  ]);
  ?>
  <?= $form->field($model, 'nama'); ?>
  <?= $form->field($model, 'file')->fileInput(); ?>
  <?php if ($model->file_id): ?>
    <div class="form-group">
      <?= Html::img(['/file', 'id' => $model->file_id]) ?>
    </div>
  <?php endif; ?>
  <div class="form-group">
    <?= Html::submitButton('Submit', ['class' => 'btn btn-primary']) ?>
  </div>
  <?php ActiveForm::end(); ?>
</div>