Say, that you are handling a multi-step process (like a complex registration form, with a number of steps the user has go through in order). You need to be able to save the current state of the process (e.g. so the user can come back to that registration form later and continue form the step where they were left off).

Obviously, you’ll probably want to give each “step” an identifier you can refer to: 1, 2, 3, 4, etc. You logic will check for this step_id (or whatever you call it) to render the appropriate data.

The question: how would you identify the stage after the final step, like the completed registration state (say, that you have to give that last “step” its own id, that’s how your logic is structured). Would it be a 0, 999, a non-integer value, something else entirely?