Popular phpExcel library does not work under new WordPress 5.7 because WP5.7 requires PHP 7.4
As a result, exporting data to an Excel file does not work.
You can switch to new, alternative, modern tools for exporting to Excel tables, or continue to use the familiar phpExcel library, but specially modified for the requirements of PHP 7.4
This modification was done independently, taking into account the flow of falling out errors. It is likely that over time, new problem areas will be identified, but at the moment they are not. All the features you need (for me anyway) work great.
There are no evil facking-hack inclusions. Guaranteed.
List of changes:
* This library is already included in the set of WordPress libraries .
Free to download.