framework/grid/GridView.php
public function renderFilters()
    {
        if ($this->filterModel !== null) {
            $cells = [];
            foreach ($this->columns as $column) {
                /* @var $column Column */
                $cells[] = $column->renderFilterCell();
            }

            return Html::tag('tr', implode('', $cells), $this->filterRowOptions);
        }

        return '';
    }
public function renderFilters()
    {
        if ($this->filterModel !== null) {
            $cells = [];
            foreach ($this->columns as $column) {
                /* @var $column Column */
                $cells[] = $column->renderFilterCell();
            }

            return Html::tag('tr', implode('', $cells), $this->filterRowOptions);
        }

        return '';
    }
Renders the filter.
@return string the rendering result.