2-3 匯出 OpenDocument 的 ods 格式

1. 使用ods物件庫，並指定不同mime type以及副檔名即可，其餘不變：

   <?php
   
   require 'vendor/autoload.php';
   
   use PhpOffice\PhpSpreadsheet\Spreadsheet;
   use PhpOffice\PhpSpreadsheet\Writer\Ods;
   
   $spreadsheet = new Spreadsheet();
   $sheet       = $spreadsheet->getActiveSheet();
   $sheet->setCellValue('A1', '這是第一格');
   
   $writer = new Ods($spreadsheet);
   header('Content-Type: application/vnd.oasis.opendocument.spreadsheet');
   header('Content-Disposition: attachment; filename="file.ods"');
   
   $writer->save("php://output");