Serializing objects with protected members

Hi, I'm trying to wrote my own serialization routines and I've found a previsible problem: protected members are not visible to my serialization routine. This is ok and it should be as is, but I've seen that PHP's serialize function have access to that members anyway, so the question is: Is there any kind of hack that I can use to access those variables from my own serialization routine? Thx. a lot in advance,