Yii2 grid sorting

I have a problem: I cannot sort my gridview.

When I click Product Name: In the URL I see: index? Sort = -product_name but nothing happens. I have not used a CRUD generator. controller

public function actionIndex()
{
    $searchModel = new CompanyProductSearch();
    $dataProvider = $searchModel->search(Yii::$app->request->queryParams);
    return $this->render('index', [
        'dataProvider' => $dataProvider,
        'searchModel' => $searchModel,
    ]);
}

      

        
        
        
      

    

SearchModel

public $searchstring;

public function rules()
{
    return [
        [['date', 'product_name', 'searchstring'], 'safe'],
    ];
}


public function scenarios()
{
    return Model::scenarios();
}


public function search($params)
{
    $array = array();
    $user = Yii::$app->user->identity;
    $product_influencer = ProductInfluencer::find()->all();
    foreach($product_influencer as $product){
        $array[] .= $product->product_id;
    }
    $query = Product::find()->where(['company_id'=>$user->company_id])
        ->andWhere(['id'=>$array])
        ->andWhere(['is not', 'shop_price', null])
        ->andWhere(['is not', 'main_category_id', null])
        ->orderBy('date DESC');

    $dataProvider = new ActiveDataProvider([
        'query' => $query,
        'pagination' => [
            'pageSize' => 10
        ],
    ]);

    $dataProvider->sort->attributes['product_name'] = [
        'asc' => ['product_name' => SORT_ASC],
        'desc' => ['product_name' => SORT_DESC],
    ];



    $this->load($params);

    if (!$this->validate()) {
        return $dataProvider;
    }

    $query->andFilterWhere([
        'product_name' => $this->product_name,
    ]);


    $query->andFilterWhere(['like', 'product_name', $this->searchstring]);

    return $dataProvider;
}

      

        
        
        
      

    

View

<?php Pjax::begin(); ?>
<?= GridView::widget([
    'summary'=>"",
    'dataProvider' => $dataProvider,
    'tableOptions' => [
        'class' => 'table table-responsive',
        'id' => 'sortable-table',
    ],
    'pager' => [
        'class' => 'common\widgets\CustomPager',
        'prevPageLabel' => '<div style="border: none" class="glyphicon glyphicon-menu-left"></div>',
        'nextPageLabel' => '<div style="border: none" class="glyphicon glyphicon-menu-right"></div>',
        'maxButtonCount' => 0,
    ],
    'columns' => [
        ['class' => 'yii\grid\CheckboxColumn',],
        [
            'class' => 'yii\grid\SerialColumn',
            'header' => 'Nr.',
        ],
        [
            'format' => 'raw',
            'label' => 'Product name',
            'attribute' => 'product_name',
            'value' => function($model){
                return Html::a($model->product_name, ['detail-product'], ['data' => [
                    'params'=>['id'=>$model->id],
                    'method' => 'get',
                ]]);
            }
        ],
        [
            'label' => 'Total earnings',
            'value' => function($model){
                return '$ 950 (test)';
            }
        ],
        [
            'label' => 'Units available',
            'value' => function($model){
                $units = \common\models\ProductInfo::findOne(['product_id'=>$model->id]);
                return $units->shop_units;
            }
        ],
    ],
]); ?>
<?php Pjax::end(); ?>

      

        
        
        
      

    

Thank!