Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
private function writeFooter()
    {
        $record = 0x0015; // Record identifier

        /* removing for now
        // need to fix character count (multibyte!)
        if (strlen($this->phpSheet->getHeaderFooter()->getOddFooter()) <= 255) {
            $str = $this->phpSheet->getHeaderFooter()->getOddFooter();
        } else {
            $str = '';
        }
        */

        $recordData = StringHelper::UTF8toBIFF8UnicodeLong($this->phpSheet->getHeaderFooter()->getOddFooter());
        $length = strlen($recordData);

        $header = pack('vv', $record, $length);

        $this->append($header . $recordData);
    }
private function writeFooter()
    {
        $record = 0x0015; // Record identifier

        /* removing for now
        // need to fix character count (multibyte!)
        if (strlen($this->phpSheet->getHeaderFooter()->getOddFooter()) <= 255) {
            $str = $this->phpSheet->getHeaderFooter()->getOddFooter();
        } else {
            $str = '';
        }
        */

        $recordData = StringHelper::UTF8toBIFF8UnicodeLong($this->phpSheet->getHeaderFooter()->getOddFooter());
        $length = strlen($recordData);

        $header = pack('vv', $record, $length);

        $this->append($header . $recordData);
    }
Store the footer caption BIFF record.