title: ActiveForm without model yii2
body: <p>I want to create <code>ActiveForm</code> without model for just in case something. I did try with <code>dynamicModel</code> but i got some error :</p>
  
  <pre><code>use yii\base\DynamicModel;
  $model = DynamicModel::validateData(compact('KOMENTAR'), [
     [['KOMENTAR'], 'string', 'max' =&gt; 128],
  ]);
  </code></pre>
  
  <p>This is the form i want to create</p>
  
  <pre><code>&lt;br&gt;
  &lt;?php $form = ActiveForm::begin([
      'method' =&gt; 'post',
  ]); ?&gt;
  
  &lt;?= $form-&gt;field($model, 'KOMENTAR')-&gt;textarea(['rows' =&gt; 6])-&gt;label(false) ?&gt;
  
  &lt;div class="form-group"&gt;
      &lt;?= Html::submitButton('POST', ['class' =&gt; 'btn btn-primary']) ?&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>This is the error</p>
  
  <pre><code>Getting unknown property: yii\base\DynamicModel::KOMENTAR
  </code></pre>