[sockwater]

You can use hard links on windows and it works (just tested). A hard link basically means that if you change either file, the other one will also be changed. You can create a hardlink on windows like this:

fsutil hardlink create newfile.php oldfile.php

Also you might want to try using junctions, which are basically directory symlinks. I don't know if this would work under apache or not.

EDIT: If you try using hardlinks, I'd like to know if the opcode caching sees them as the same file or separate files.