Xampp OneDrive php bug
There's an important bug in Windows 10 May 2019 Update.
It would seem that the new "Files on Demand" feature of OneDrive in the Windows May 2019 Update causes issues with PHP's ability to open files and work with Xampp or other PHP offline server.
This happended before (after fall update) and was fixed later, but now, the bug is here again (after May Update).
Any attempt to iterate through files in a folder, or even simply do a "require" results in PHP somehow not being able to see them. This applies even if the files are locally available on the PC, the only thing needed to trigger this is to have the source file located somewhere within the OneDrive folder.
Moving the source file to any other folder (outside OneDrive) makes things work normally.
Please read more here: https://bugs.php.net/bug.php?id=75384