title: Yii2 : Get Sum In footer of gridview
body: <p>I'm new here that I can't comment <a href="https://stackoverflow.com/questions/26852453/yii2-getting-sum-of-a-column">here</a> </p>
  
  <p>and I have a problem when I try to Get sum in the footer . </p>
  
  <p>my code in controller :</p>
  
  <pre><code>$searchModel = new ReceiptsSearch();
  $sum = new ReceiptsSearch();
  $dataProvider = $searchModel-&gt;search(Yii::$app-&gt;request-&gt;queryParams);
   return $this-&gt;render('index', [
     'searchModel' =&gt; $searchModel,
     'dataProvider' =&gt; $dataProvider,
     'sum'=&gt;$sum,
     ]);
  </code></pre>
  
  <p>my SearchModel Code  : </p>
  
  <pre><code>public function search($params)
  {
      $query = Receipts::find();
      $sum = $query-&gt;sum('price');
      $dataProvider = new ActiveDataProvider([
          'query' =&gt; $query,
      ]);
  
      $this-&gt;load($params);
  
      if (!$this-&gt;validate()) {
          return $dataProvider;
      }
      $query-&gt;joinWith('patient'); 
      $query-&gt;andFilterWhere([
         'id' =&gt; $this-&gt;id,
         'price' =&gt; $this-&gt;price,
         'reg_date' =&gt; $this-&gt;reg_date,
      ]);
      $query-&gt;andFilterWhere(['like','patient.patient_name',$this-&gt;patient_id]);
  
      return $dataProvider;$sum;
  }
  </code></pre>
  
  <p>my view page </p>
  
  <pre><code>&lt;?= GridView::widget([
  
      'dataProvider' =&gt; $dataProvider,$sum,
  
      'filterModel' =&gt; $searchModel,
      'showFooter' =&gt; true,
      'columns' =&gt; [
  
          ['class' =&gt; 'yii\grid\SerialColumn'],
  
          [
          'attribute'=&gt;'patient_id',
          'value'=&gt;'patient.patient_name'
          ],
          'price',
          ],
          [
          'attribute' =&gt; 'sum',
          'footer' =&gt; 'sum',
          ],
          ['class' =&gt; 'yii\grid\ActionColumn'],
      ],
      ]); 
  ?&gt;
  </code></pre>
  
  <p>the message shown is : </p>
  
  <blockquote>
    <p>Setting unknown property: yii\grid\GridView::0</p>
  </blockquote>