PHP: Failed opening required filepath in Unknown on line 0

I ran into this error message while working on a personal project. I had set up the code in my Microsoft OneDrive folder to sync it between my laptop and my desktop. I suspected the error might have something to do with OneDrive, so I copied my code to another folder on my computer. Sure enough, it worked perfectly. Finally, I discovered the problem. It was a setting in OneDrive called "Files On-Demand". What I suspect is that the files were simply just 0-byte stubs on my desktop. So when PHP requested them, it failed. Once I unchecked this box and OneDrive downloaded all of the necessary files, it worked just fine.