PHPOffice / PhpSpreadsheet

    /**

     * Write Internal SUPBOOK record

     */

    private function writeSupbookInternal()

    {

        $record    = 0x01AE;   // Record identifier

        $length    = 0x0004;   // Bytes to follow

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

        $data      = pack("vv", $this->spreadsheet->getSheetCount(), 0x0401);

        return $this->writeData($header . $data);

    }

    /**

     * Writes the Excel BIFF EXTERNSHEET record. These references are used by

     *

     * @return string

     */

    private function writeCountry()

    {

        $record = 0x008C;    // Record identifier

        $length = 4;         // Number of bytes to follow

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

        /* using the same country code always for simplicity */

        $data = pack('vv', $this->countryCode, $this->countryCode);

        //$this->append($header . $data);

        return $this->writeData($header . $data);

    }

    /**

     * Write the RECALCID record

     *

     * @return string

     */

    private function writeRecalcId()

    {

        $record = 0x01C1;    // Record identifier

        $length = 8;         // Number of bytes to follow

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

        // by inspection of real Excel files, MS Office Excel 2007 writes this

        $data = pack('VV', 0x000001C1, 0x00001E667);

        return $this->writeData($header . $data);

    }

    /**

     * Stores the PALETTE biff record.

     *

     * @param integer $count The number of external sheet references in this worksheet

     */

    private function writeExterncount($count)

    {

        $record = 0x0016;          // Record identifier

        $length = 0x0002;          // Number of bytes to follow

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

        $data   = pack("v", $count);

        $this->append($header . $data);

    }

    /**

     * Writes the Excel BIFF EXTERNSHEET record. These references are used by