Sorry folks, I've been tied up. Will do so later today.
If you mean the whole page (i.e. including, e.g. the site menu, etc), then what @netcarver said. die() will also work. Yes, if in a module halt() will not work. In some contexts, another process might be returning content as well. If exit() does not work for you, please show us your whole code and/or tell us more about your context.