How was the photo taken on a white background?

PS, even if shooting in space, the background can't be pure white without overexposure.

The prophase and anaphase are not so complicated, and the shooting doesn't have to have a white background, as long as the shoes are not blocked by anything. In this photo, the surface of your shoes seems to have a red reflection. Click with a pen in PS, load the pen selection, reverse the selection and fill it with white.

It's that simple.