If I understand this regexp right, the deprecation error will be triggered for example for numbers like123.45 but it shouldn't. We'd need to test explicitly the presence of the comma.

yeah, the order of regexps should be changed, to match the standard regex first to handle the case of values matching the spec
This will require to duplicate the linereturn (float) str_replace(array(',', '_'), '', $scalar); instead of using a fallthrough, but this is not an issue.

These cases are already handled further up where we have theis_numeric() check (and we have tests covering that this is working).

As@javiereguiluz said, this deprecation will be triggered with123.45, which is not correct. IMO, the* should be replaced with a+ to ensure that a, is indeed used.

actually, the+ won't be enough ; we need to test that[0-9]+,[0-9]*(?:\.[0-9_]+)? matches this I think (but I'm not too sure too)

@Taluu but it's true what@xabbuh said: this is handled in the code above thiscase: and there are tests about this and they pass.

But it should be triggered for123.45_67 though (I think), as there are no cases for that above this case, and that is valid though. And I think a_ may have been forgotten in the part before the. actually.

IMO, we should do astrpos test to test that a, is indeed in the match, and then only trigger the deprecation

@Taluu You are right. I opened#18858 which should fix this issue.

And I think a_ may have been forgotten in the part before the. actually.

I think it's okay the way it is. We only introduced the_ for 3.2 and I think people should not start mixing_ and, then. If they want to use_, they should just move away from, as well.