title: Yii2 populate update form with values stored in array
body: <p>I have created a form with the following fields and use json encode before saving to a single database field.</p>
  
  <p>Now I need to populate the fields when using the update form however I am unsure as i can't find any yii2 example. </p>
  
  <pre><code>&lt;?= $form-&gt;field( $model, 'seo_information[field1]' )
            -&gt;textInput( [ 'maxlength' =&gt; 255 ] )
            -&gt;label('Array Field 1) ?&gt;
  
  &lt;?= $form-&gt;field( $model, 'seo_information[field2]' )
           -&gt;textInput( [ 'maxlength' =&gt; 255 ] )
           -&gt;label('Array Field 2') ?&gt;
  
  &lt;?= $form-&gt;field( $model, 'seo_information[field3]' )
           -&gt;textInput( [ 'maxlength' =&gt; 255 ] )
           -&gt;label('Array Field 3') ?&gt;
  </code></pre>
  
  <p>Controller Create Code</p>
  
  <pre><code>public function actionCreate()
  {
      $model = new Article();
      $model-&gt;user_id = Yii::$app-&gt;user-&gt;id;
  
      if ($model-&gt;load(Yii::$app-&gt;request-&gt;post())) 
      {
          $seo_information = $_POST['Article']['seo_information'];
          $model-&gt;seo_information = json_encode($seo_information); 
          $model-&gt;save();
          return $this-&gt;redirect(['view', 'id' =&gt; $model-&gt;id]);
      } 
      else 
      {
          return $this-&gt;render('create', [
              'model' =&gt; $model,
          ]);
      }
  }
  </code></pre>