[pilif]

Same goes for <%= which has been used by people for years to output HTML content.

Changing echo; to encode entities when used from within a web server SAPI (so not on the command line) would not cause more or less hassle per app than changing <%= to encode entities by default.

Of course the overall PHP code base is much bigger than the rails code base, so there would be more people affected. But for the individual application developer, there's no difference in amount of work whether <%= suddenly starts escaping or echo; does.