👍 But the name sounds strange - I originally suggested something like PREG_SUBPATTERN_UNMATCHED_NULL or PREG_UNMATCHED_AS_NULL, how about that?

Agree with @Majkl578 on name, and I like PREG_UNMATCHED_AS_NULL (but I don't care enough to bikeshed on it)

I see you've updated (essentially reverted from prior commit) the tests dealing with unmatched subpatterns, but would you mind adding a test which uses the constant?

I second PREG_UNMATCHED_AS_NULL and think its very important to get the naming right (always).

Updated
Tests with the const already exist, see bug61780*.phpt

Oh, weird, dunno how I missed the tests before. Anyway, thumbs up from me.

Could this be merged please? That'd help us try 7.2 as it removes the BC break. Then if the new part needs improvement, it'll be open to another PR.

LGTM, will merge it asap

Comment on behalf of remi at php.net:

Merged, thanks

ping @cmb69 FYI since you wanted to have another behavior when the flag (another one) is passed.
Thanks @remicollet for merging.

@nicolas-grekas Thanks for the ping. Since others like this PR, it's okay for me to have this behavior. :)