PHP-da massivlarni aylantirish

Задание 1

Berilgan massiv:

php<?php
  $arr = ['a' => 1, 'b' => 2, 'c' => 3];
?>

Undagi kalit va qiymatlarni almashtiring.

Задание 2

Berilgan massiv:

php<?php
  $arr = [1, 2, 3, 4, 5];
?>

Undan quyidagi massivni yarating:

php<?php
  [5, 4, 3, 2, 1]
?>