I have a simple HTML file upload form:

<form enctype="multipart/form-data" method="post">
    <input name="description" type="text">
    <input name="file" type="file">
    <button type="submit">Submit</button>
</form>

When the user submits - it sends an AJAX post request to my php script that is running in an Azure App Service (Azure Function). The PHP script saves the file to the server like this:

<?php
file_put_contents($filename, $data);

This is working perfectly for all files - except .xlsx excel files.

When trying to open the excel file that got saved on the server - I receive the following error in excel: We found a problem with some content in 'test-excel-file.xlsx'. Do you want to try to recover as much as we can?

Anyone have any ideas why the .xlsx file is somehow getting corrupted when being saved to the server? I did some testing and can see that when I open both the original excel file and the newly saved excel file in a text editor - the content is the same. So why is Excel complaining?

In fact, I can create a brand new workbook in excel with a sample row of data - save this file. Then open it in a text editor and copy/paste the contents to a new file and the same error occurs. So I really don't think it's an issue with file_put_contents.

So what is the issue with trying to save Excel (.xlsx) file contents to a new .xlsx file? Anyone have any suggestions? Thank you for your time.

CodePudding user response：

The solution was to not host this PHP script in an Azure Function, because Azure Functions do not expose the $_FILES global. Without access to $_FILES, I had to parse the multipart form request manually, which was somehow corrupting complex files.

So I moved the script over to one of our regular Azure App Service's where I could then access the $_FILES global and didn't need to do any manual parsing of the file contents.