grid\GridView $filterModel

The model that keeps the user-entered filter data. When this property is set, the grid view will enable column-based filtering. Each data column by default will display a text field at the top that users can fill in to filter the data.

Note that in order to show an input field for filtering, a column must have its yii\grid\DataColumn::$attribute property set or have yii\grid\DataColumn::$filter set as the HTML code for the input field.

When this property is not set (null) the filtering feature is disabled.