<?php
$x = array(
  'z' => 8,
  'r' => 2,
  'a' => 10,
  'q' => 99,
  'x' => 16,
  'd' => 1
);
$y = array(
  'z' => 8,
  'r' => 2,
  'a' => 10,
  'q' => 99,
  'x' => 16,
  'd' => 1
);

asort($x, SORT_NUMERIC);
$x = array_reverse($x, true);

arsort($y, SORT_NUMERIC);

var_dump($x, $y);

array(6) {
  ["q"]=>
  int(99)
  ["x"]=>
  int(16)
  ["a"]=>
  int(10)
  ["z"]=>
  int(8)
  ["r"]=>
  int(2)
  ["d"]=>
  int(1)
}
array(6) {
  ["q"]=>
  int(99)
  ["x"]=>
  int(16)
  ["a"]=>
  int(10)
  ["z"]=>
  int(8)
  ["r"]=>
  int(2)
  ["d"]=>
  int(1)
}