PHP force downloading .xlsx file corrupt - php

Question

I am working on a site that allows teachers to upload documents and students download them. However, there is a problem. Microsoft Word (.docx) files download perfectly, but when downloading an excel (xlsx) file, excel gives a "This file is corrupt and cannot be opened" dialog. Any help with this would be greatly appreciated!
My download code is as follows:
case 'xlsx':
header('Content-type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
header('Content-Disposition: attachment; filename="' . $filename . '"');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Pragma: no-cache');
readfile('./uploads/resources/courses/' . $filename);
break;

Answer 1

I have this problem and was the BOM.
How to notice it
unzip: Checking the output file with unzip, I saw a warning at the second line.
$ unzip -l file.xlsx
Archive: file.xlsx
warning file: 3 extra bytes at beginning or within zipfile
...
xxd (hex viewer): I saw the first 5 bytes with the following command
head -c5 file.xlsx | xxd -g 1
0000000: ef bb bf 50 4b PK...
Notice the 3 first bytes ef bb bf that's BOM!
Why?
Maybe a php file with BOM or a previous output from a library.
You have to find where is the file or command with the BOM, In my case and right now, I don't have time to find it, but I solve this with output buffer.
<?php
ob_start();
// ... code, includes, etc
ob_get_clean();
// headers ...
readfile($file);

Answer 2

this works fine on my local xampp setup regardless of extension so from my point of view no case statement is needed unless i'm missing something
i've tested with docx, accdb, xlsx, mp3, anything ...
$filename = "equiv1.xlsx";
header('Content-type: application/octet-stream');
header('Content-Disposition: attachment; filename="' . $filename . '"');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Pragma: no-cache');

Answer 3

try this:
header("Content-Disposition: attachment; filename=\"$filename\"");
header("Content-Type: application/vnd.ms-excel");

Answer 4

try:
<?
//disable gzip
#apache_setenv('no-gzip', 1);
//set download attachment
header('Content-Disposition: attachment;filename="filename.xlsx"');
//clean the output buffer
ob_clean();
//output file
readfile('filepath/filename.xlsx');
//discard any extra characters after this line
exit;
?>

Answer 5

Try adding a additional header
header('Content-Length: ' . filesize('./uploads/resources/courses/' . $filename));

Answer 6

Probably it's very misleading information given by Windows and has nothing to do with the code, Excel library, or server, and the file itself is a proper one. Windows blocks opening some files downloaded from the Internet (like .xlsx) and instead of asking whether you want to open an insecure file, it just writes that the file is corrupt. In Windows 10, one needs to right-click the file and select "Unblock" (you can read more for example here: https://winaero.com/blog/how-to-unblock-files-downloaded-from-internet-in-windows-10/)