Connecting shower drain to toilet drain?

I am thinking of adding a shower in a bathroom that is on a slab. I would like to use PVC pipe from the shower drain and connect the same to copper drain pipe of the toilet. They will be just next to each other and will not need lot of digging. What is the best way to do it?I am thinking of putting a rubber T to make a mechanical connection but I am doubtful if that is a good idea under a slab. I can use copper pipe but I have always found it difficult to weld 2" copper pipe. I am good at welding 1/2" copper pipe. Any suggestion will be helpful.