My son's iPhone is overheating to the point where when he touches the top button he is going to be burned. Also, the camera turns itself on and the top left corner turns purple with black lines?

Make an appointment and take it in to Apple. If it is getting that hot, something must be severely shorting internally to generate that much heat. Apple will diagnose it for no charge. If you are under warranty and it is a warranty issue, they will replace it. Otherwise, you may have to pay the out of warranty exchange fee, but you'd get a like-new factory refurbished device in exchange.

I would turn it off and leave it off until you can get a hardware diagnosis done by Apple - that sort of heat has to be from an internal, physical fault.