Example Kartik gridview with select2 filter column

controller_action.php

    /**
     * For Kartic select2 widget
     * @param type $q
     * @param type $id
     * @return type
     */
    public function actionLotList($q = null, $id = null) {
        \Yii::$app->response->format = \yii\web\Response::FORMAT_JSON;
        $out = ['results' => ['id' => '', 'text' => '']];
        if (!is_null($q)) {
            $query = new Query;
            $query->select('id, name AS text')
                ->from('stock_lot')
                ->where(['like', 'name', $q])
                ->limit(20);
            $command = $query->createCommand();
            $data = $command->queryAll();
            $out['results'] = array_values($data);
        }
        elseif ($id > 0) {
            $out['results'] = ['id' => $id, 'text' => StockLot::find($id)->name];
        }
        return $out;
    }

Example_kartik_gridview_select2_ajax.php

            [
                'attribute'=>'lot_id',
                'value'=>'lot.name',
                'label'=>'Control No.',
                'filterType'=> GridView::FILTER_SELECT2,
                'filterWidgetOptions'=>[
                    'initValueText'=>'hello',
                    'options' => ['placeholder' => 'Search for a city ...'],
                    'pluginOptions' => [
                        'allowClear' => true,
                        'minimumInputLength' => 1,
                        'language' => [
                            'errorLoading' => new JsExpression("function () { return 'Waiting for results...'; }"),
                        ],
                        'ajax' => [
                            'url' => Url::to(['/stock/stock-lot/lot-list']),
                            'dataType' => 'json',
                            'data' => new JsExpression('function(params) { return {q:params.term}; }')
                        ],
                        'escapeMarkup' => new JsExpression('function (markup) { return markup; }'),
                        'templateResult' => new JsExpression('function(lot) { return lot.text; }'),
                        'templateSelection' => new JsExpression('function (lot) { return lot.text; }'),
                    ],
                ]
            ],