Create a Money class, or use one off the shelf. It should store the currency and the amount. There are a few popular ways of storing amounts (integer cents, fixed decimal) but it should not be exposed outside the Money class.
There's plenty of good advice in this subthread for how to represent currency inside your Money abstraction, but whatever you do, keep it hidden. If you pass around numbers as currency values you will be in for a world of pain as your application grows.
There's plenty of good advice in this subthread for how to represent currency inside your Money abstraction, but whatever you do, keep it hidden. If you pass around numbers as currency values you will be in for a world of pain as your application grows.