grid\DataColumn $filter

The HTML code representing a filter input (e.g. a text field, a dropdown list) that is used for this data column. This property is effective only when yii\grid\GridView::$filterModel is set.

• If this property is not set, a text field will be generated as the filter input;
• If this property is an array, a dropdown list will be generated that uses this property value as the list options.
• If you don't want a filter for this data column, set this value to be false.