Altrea -- Thanks for the reply. I discovered that in Big Sur, as opposed to Catalina, in order to run files in a subdirectory of the localhost root directory, I have to include the name of the localhost root directory. i.e.:
http://localhost/Sites/sub-directory/Where "Sites" is the local name of the localhost RootDirectory.
In Catalina and before, the name of the root directory was not require. i.e.:
http://localhost/sub-directory/with localhost pointing to the root directory.
I had to add "Sites" to the directory path in all my editor setup files for each site to get it to work.
I don't know if this is an xampp thing or a Big Sur thing. I would suspect it is actually xampp that made this change, though I didn't read about it on the website anywhere. Of course, Apple makes you work to discover how they change things, especially related to web servers. I still haven't gotten Apples installed version of php to work.
--Kenoli