Fix accessing of overridden private property in get_object_vars()

[iluuu1994]

Fixes GH-20177

[iluuu1994]

One side-effect in this PR is that this will also affect foreach ($this as $prop). https://3v4l.org/rCSNe#v8.4.13 Doesn't seem obvious what the "right" solution is here. Another approach might be to adjust just get_object_vars() to skip properties that have already been set, i.e. ones that were set by the parent class.

[nielsdos]

Right. I understand the BC concern. Although I'd also expect that get_object_vars() and foreach() behaves consistently.

[iluuu1994]

@nielsdos Right. Maybe it's ok to merge this for master then. The docs say:

https://www.php.net/manual/en/language.oop5.iterations.php

By default, all visible properties will be used for the iteration.

I guess the child property can be thought of as "reverse shadowed". Though I don't think these semantics were ever properly described or even considered.

[nielsdos]

Agreed. This is kinda underspecified.

[iluuu1994]

Pinging @bwoebi, as he has had opinions on previous, similar issues. ^^