I'm not 100% sure this is a bug. utf8_normalizer_test uses call-time pass by reference to call_user_func, twice. I received warnings about that while trying to run the test suite. I notice that http://us3.php.net/call_user_func states that call_user_func parameters are not passed by reference, which on one hand I suppose could mean they are always copied, and on the other hand if call-time pass by reference actually works then using it despite warnings may yield memory savings.