Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Writer/Xls/BIFFwriter.php
protected function storeEof()
    {
        $record = 0x000A; // Record identifier
        $length = 0x0000; // Number of bytes to follow

        $header = pack('vv', $record, $length);
        $this->append($header);
    }
protected function storeEof()
    {
        $record = 0x000A; // Record identifier
        $length = 0x0000; // Number of bytes to follow

        $header = pack('vv', $record, $length);
        $this->append($header);
    }
Writes Excel EOF record to indicate the end of a BIFF stream.