Unless the opcache is smart enough to optimize the if block you are never going to get the full benefit of the opcode cache as you are conditionally including files.
Actually I don't see any reason why conditional include would hurt performance in any way - it shouldn't hurt compile-time binding and it shouldn't hurt any opcode cache that does per-file caching (and all those I know do that).
-- Stanislav Malyshev, Zend Products Engineer [EMAIL PROTECTED] http://www.zend.com/
