This is targeting 8.0.
`$arg` seems like a poor choice of a name,
especially if the function were to have arguments added.
In many cases, the php.net documentation already has $array for these functions.
E.g. https://www.php.net/manual/en/function.array-intersect.php
I'd assume that since named arguments was added to 8.0 near the feature freeze,
PHP's maintainers had planned to make the names consistent
and gradually use the same name for docs and implementation.
PHP requires integer typehints to be written "int" and does not
allow "integer" as an alias. This changes type error messages to
match the actual type name and avoids confusing messages like
"must be of the type integer, integer given".
