protected function compileTableFooter()
    {
        $footer = [];
        foreach ($this->collection->all() as $row) {
            if (is_array($row->footer)) {
                $footerAttr = $this->html->attributes(array_only($row->footer,
                    ['class', 'id', 'title', 'width', 'style', 'data-class', 'data-hide']));
                $title = isset($row->footer['title']) ? $row->footer['title'] : '';
                $footer[] = '<th ' . $footerAttr . '>' . $title . '</th>';
            } else {
                $footer[] = '<th>' . $row->footer . '</th>';
            }
        }

        return $footer;
    }