Hanging mirrors in some places can also be said to be a folk custom. As long as people believe in ghosts and gods, no matter what happens at home, they will hang a mirror at the door. It is a kind of psychological comfort to have ghosts to drive away ghosts and keep good luck, just like putting up a door in the New Year.
However, what I really know is that I don't hang a mirror at the door. I think hanging a mirror can not only reflect bad luck, but also ruin my Feng Shui.
Be sure to use it carefully!