Due to privacy conditions in certain regions of the world, it is relatively difficult to turn off the shutter noise on the iPhone. In fact, there is only one way to do this and it is the trivial way. Simply flip the mute switch on and your camera shutter sound will go away! There is no other way to do this as Apple is following regional privacy conditions from around the world.
If you manage to find another way of doing this, please post in the comments below!