My iPhone 4 won't charge and gets very hot?

I've had my iPhone 4 for about 2 years, but recently since I went abroad its been having troubles.
It won't charge longer than about 40%, but then it looses charge really quickly. It also heats up allot on the back of the phone, and the torch used to be constantly on dimly but that's stopped now.

What is the problem and how is it fixed?
, thank you

You bought a product from a brand with a purposely limited life-cycle.

Buy something different.