(geek level: 90%)
If you set PHP’s include_path to include a directory for which Apache doesn’t have read permission, it fails in a strange way. In the Apache error log:
[…] Failed opening required ‘chorus/Paths.php’ (include_path=’0’) […]
include_path=’0’? Strange. No other errors or warnings are logged by PHP.
Fix permissions, and the include_path works perfectly.
Hopefully this post will turn up on a Google search for the next unfortunate person who hits this bug.