empty list removed

Hello,

3ae0b14dd0 removed the list of empty things.

The documentation now says "A variable is considered empty if it does not
exist or if its value equals false." Great, and which values do that?

The commit message says: "To avoid duplication, we refer to falsey values
instead."

If this is a duplicate, we need to link to the list where it exists. If it
is only a duplicate of scattered information all around and the list
doesn't exist anywhere, this commit needs to be reverted and "SimpleXML
objects from empty tags" added to the list. I would vastly prefer this one
but I am not here to start an edit war. Let's discuss first :)

Also, if those objects are worth a special case then
https://www.php.net/manual/en/types.comparisons.php needs to be fixed too.
And yes you can -- kind of -- glean the list of empty things from this page
but it's a big mental effort.

Thanks

Karoly Negyesi