浏览器下载先前的文件版本(从缓存中下载吗?)

我正在使用PHPExcel生成要下载的电子表格。

<?php
    $objPHPExcel = new PHPExcel();
    $emailReport = 'tmp/company.xls';
    // Remove previous file if it exists.
    $testdel=unlink($emailReport);
    if(!$testdel){
        echo "Unable to remove previous Spreadsheet<hr/>";
    }
    echo '<a href="'.$emailReport.'" class="dbutton">Download Spreadsheet</a><hr/>';
    $objPHPExcel->getActiveSheet()->setCellValueByColumnAndRow(1, 1,'Old Value');
    $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
    $objWriter->save($emailReport);
    ?>

一切都很好。

电子表格已创建,并将文本保存在单元格A1中。

But if I change the php file, perhaps by changing $objPHPExcel->getActiveSheet()->setCellValueByColumnAndRow(1, 1,'Old Value');to $objPHPExcel->getActiveSheet()->setCellValueByColumnAndRow(1, 1,'New, Improved Value'); I'm expecting the new spreadsheet to contain "New, Improved Value" in cell A1, but when I click the link to download it, the version of the spreadsheet that is downloaded contains the old value.

但是,当我使用FTP下载文件时,该文件确实已更新。

大概浏览器将文件保存在缓存中?

如何确保下载了正确的版本?