* The array "subject" of a function gets called $array.
* Further parameters should be self-descriptive if used
as a named parameter, and a full word, not an abbreviation.
* If there is a "bunch more arrays" variadic, it gets
called $arrays (because that's what was already there).
* A few functions have a variadic "a bunch more arrays,
and then a callable", and were already called $rest.
I left those as is and died a little inside.
* Any callable provided to an array function that acts
on the array is called $callback. (Nearly all were already,
I just fixed the one or two outliers.)
* array_multisort() is beyond help so I ran screaming.
This is targeting 8.0.
`$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.
