PHP_excel: export to xlsx loads successfully, but when we open it, it shows a warning that Excel has detected unreadable content

Question

I am using php_excel to export to xlsx. In my application, I am using a template. When I download, the xlsx file loads normally, but when we open it, the following warning is displayed:

" Excel detected unreadable content in" project_report (3) .xlsx. "Would you like to restore the contents of this workbook? If you trust the source of this workbook, click Yes ."

If I click yes, it opens the file correctly.

And one more thing when I attach the downloaded file to the mail. And if I open it, sing the Google Spread sheet, it will say that the bad format does not open.

therefore, if someone knows the reason, please suggest me to solve this problem.

Answer 1

check your headers, here are mine:

header("Pragma: public"); header("Expires: 0"); header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); header("Content-Type: application/force-download"); header("Content-Type: application/octet-stream"); header("Content-Type: application/download");; header("Content-Disposition: attachment;filename=$filename"); header("Content-Transfer-Encoding: binary"); $objWriter->save('php://output'); 

check output (spaces before <?php forgot echo ? etc.