[php] PHP Fatal Error Failed opening required File

Just in case this helps anybody else out there, I stumbled on an obscure case for this error triggering last night. Specifically, I was using the require_once method and specifying only a filename and no path, since the file being required was present in the same directory.

I started to get the 'Failed opening required file' error at one point. After tearing my hair out for a while, I finally noticed a PHP Warning message immediately above the fatal error output, indicating 'failed to open stream: Permission denied', but more importantly, informing me of the path to the file it was trying to open. I then twigged to the fact I had created a copy of the file (with ownership not accessible to Apache) elsewhere that happened to also be in the PHP 'include' search path, and ahead of the folder where I wanted it to be picked up. D'oh!