I'm not sure that this is suitable for posting... but it might help-out someone.
I was unable to find the source of my inclusion error on the forums ("Warning: Failed opening '/usr/local/apache/htdocs/PHP/TEMP/increment_operators.php' for inclusion (include_path='.:/usr/local/lib/php') in Unknown on line 0").
Luckily, I did feret-out the culprit. In my absolute brilliance (I hope that you smell the sarcasm), I changed my umask to 066. So, PHP lacked permission to view the file. Sheer intellectual gold. I chmod'ed to 644 and all is well.
Hopefully, you're all smarter than I.