Thank you all for the comments. The naming brought some constructive discussion.
My preferred solution would be inconsistent PHP_ROUND_AWAY_FROM_ZERO and PHP_ROUND_TOWARD_ZERO as those are friendlier to the most of developers and are not possible to mistake with other modes. I would go even one step further and create aliases for NumberFormatter constants to have the naming consistent. > Introducing a brand-new RoundingMode enum (using union types) I > suggested in my first email would nicely solve the naming problem and > would also make the API more obvious to use due to stronger typing in > the long run. That's also interesting idea and I would push it, however I'm afraid about the naming of namespace. I recollect some of the RFCs were rejected simply because of the namespace. If there is a guideline for the namespace of core functions I would willingly get familiar to it. Otherwise, I don't want to open Pandora box only because of the namespace of Enum. It would also bring BC to the function, unless we would accept both enum and old constants. Kind regards, Jorg