In php.ini, I have:
session.save_path="C:\DOCUME~1\pjs9486\LOCALS~1\Temp\php\session"
I was cleaning out the temp directory, and deleted the php directory. Session stuff quit working. I re-created the php directory. Still no luck. I re-created the session directory in the php directory, and session stuff resumed working.
I would have expected session_start() to have re-created directories in the path, if they didn't exist, but, it doesn't.
Note to self: Don't do that again!!!!