Refactoring create_function for php 7.2

I need to refactor a piece of php code to work with 7.2 but i am not sure if the way i did it is correct. I could use some info about it. This is the old code

    private function sortByFields($field, &$array)
    {
        usort($array, create_function('$a, $b', '
            $a = $a["' . $field . '"];
            $b = $b["' . $field . '"];

            if ($a == $b) return 0;

            return ($a < $b) ? -1 : 1;
        '));

        return true;
    }

And this is the code i refactored for 7.2

    private function sortByFields($field, &$array)
    {
        usort($array, function ($a,$b) {
            $a = $a["' . $field . '"];
            $b = $b["' . $field . '"];

            if ($a == $b) return 0;

            return ($a < $b) ? -1 : 1;
        });

        return true;
    }

Is it correct or did i mess up ?

Answer

You missed out on the “use” part so the function body does not know about the $field and messed up the $field array keys – see below:

private function sortByFields($field, &$array)
{
    usort($array, function ($a,$b) use ($field) {
        $a = $a[$field];
        $b = $b[$field];

        if ($a == $b) return 0;

        return ($a < $b) ? -1 : 1;
    });

    return true;
}