Box\Spout\Writer\XLSX\Helper\FileSystemHelper::createWorkbookFile PHP Method

    public function createWorkbookFile($worksheets)
    {
        $workbookXmlFileContents = <<<EOD
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">
    <sheets>
EOD;
        /** @noinspection PhpUnnecessaryFullyQualifiedNameInspection */
        $escaper = \Box\Spout\Common\Escaper\XLSX::getInstance();
        /** @var Worksheet $worksheet */
        foreach ($worksheets as $worksheet) {
            $worksheetName = $worksheet->getExternalSheet()->getName();
            $worksheetId = $worksheet->getId();
            $workbookXmlFileContents .= '<sheet name="' . $escaper->escape($worksheetName) . '" sheetId="' . $worksheetId . '" r:id="rIdSheet' . $worksheetId . '"/>';
        }
        $workbookXmlFileContents .= <<<EOD
    </sheets>
</workbook>
EOD;
        $this->createFileWithContents($this->xlFolder, self::WORKBOOK_XML_FILE_NAME, $workbookXmlFileContents);
        return $this;
    }