Fix GH-21583: SimpleXML empty element incorrectly casts to true.

[devnexen]

No description provided.

[ndossche]

This changes very long standing behaviour. The current behaviour is here since PHP 5.1.x. PHP 5.0.x had different behaviour, closer to what you propose in the PR but not quite the same.
Since this is changing such old behaviour this can only go into master.
I'm also not so sure whether this should be fixed in the code or if this is a documentation mistake. The new code makes more sense than what it was because now it is similar to a string cast followed by a bool cast.
It raises the question though why the current behaviour is what it is.

[devnexen]

This changes very long standing behaviour. The current behaviour is here since PHP 5.1.x. PHP 5.0.x had different behaviour, closer to what you propose in the PR but not quite the same. Since this is changing such old behaviour this can only go into master. I'm also not so sure whether this should be fixed in the code or if this is a documentation mistake.

If that helps, I would rather go towards doc fix.

[iluuu1994]

I agree. While peculiar, this doesn't look like accidental behavior. Changing might be ok, but not in a patch.

I'd also add that I think falsy objects are questionable, though I understand that's nothing new in this PR.

[Girgias]

I agree. While peculiar, this doesn't look like accidental behavior. Changing might be ok, but not in a patch.

I'd also add that I think falsy objects are questionable, though I understand that's nothing new in this PR.

Especially because the SimpleXML behaviour is prone to be quite buggy. I wonder if we should deprecate this feature for SimpleXML.

[ndossche]

Just change the docs to the sample that casting a new GMP(0) instance results in false or something like that. It's intuitive enough and requires less words than currently.