Your phal is surviving on the arial roots.
If you are a chronic overwaterer, I would repot it in a bark mix(soak your bark at least 24 hours). I still prefer moss or a peat mix,but that is my preference.
Clean off the brown rotten roots by pulling the outer layer off,leaving the wirey stem (that gives some support to the orchid )while it grows new roots.
I dust the remaining areas with a powdered rooting hormone(some also contain a fungicide, which is good). If you soak the arial roots and get them pliable,you might be able to get them in the mix.... I have done this with no ill effects! If not leave them alone and keep them misted.
Place it out of direct bright light for a few days. It is not beyond saving.
I received a violecia ,that only had 2 one inch long roots..pitiful leaves and it is growing a new leaf and I can see new roots starting..so do not give up and GOOD LUCK!