title: yii2 - model load function does not set some model attributes
body: <p>I'm working on a PHP Yii2 application. I have a strange problem with yii2 <code>yii\base\Model.load</code> function. Here is my problem:</p>
  
  <p>I have a form model called <code>PaymentIncreaseBalanceForm</code> like below:</p>
  
  <pre><code>class PaymentIncreaseBalanceForm extends yii\base\Model {
       public $amount;
       public $receiptNumber;
       public $description;
       ...
  }
  </code></pre>
  
  <p>Here is part of my view file:</p>
  
  <pre><code>&lt;?= $form-&gt;field($model, 'amount')-&gt;textInput(['maxlength' =&gt; true]) ?&gt;
  
  &lt;?= $form-&gt;field($model, 'receiptNumber')-&gt;textInput(['maxlength' =&gt; true]) ?&gt;
  
  &lt;?= $form-&gt;field($model, 'description')-&gt;textarea(['rows' =&gt; 6]) ?&gt;
  </code></pre>
  
  <p>And this is my controller action:</p>
  
  <pre><code> public function actionIncreaseBalance()
   {
        $modelForm = new PaymentIncreaseBalanceForm();
        if ($modelForm-&gt;load(Yii::$app-&gt;request-&gt;post()))
        {
                //some logic
        }
  
         return $this-&gt;render('increase-balance', [
                  'model' =&gt; $modelForm,
        ]);
    }
  </code></pre>
  
  <p>After submitting the form, I logged <code>Yii::$app-&gt;request-&gt;post()</code> with <code>die()</code> and all three parameters <code>amount</code>, <code>receiptNumber</code>, <code>description</code> exist in the post with their right values(every thing is right). But after calling <code>$modelForm-&gt;load</code> function, this is my model attributes:</p>
  
  <pre><code>$amount =&gt; 1000,
  $receiptNumber =&gt; 887412141,
  $description =&gt; NULL,
  </code></pre>
  
  <p><code>$description</code> always is NULL! I don't know what is the problem with this field. Is there any problem with my code?</p>