Pressbooks\Modules\Export\Mpdf\Pdf::getHeader PHP Method

    function getHeader($display = true, $content = '')
    {
        // bail early
        if (false == $display) {
            return '';
        }
        // override
        $header = apply_filters('mpdf_get_header', $content);
        //sanitize
        $header = \Pressbooks\Sanitize\filter_title($header);
        return $header;
    }