How to sort associative arrays in descending order, according to the key in php ?

<?php

 $names= array("Mohamed"=>"", "Ahmed"=>"", "Karem"=>"");

krsort($age);

?>

<?php

$fruits = array("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");

ksort($fruits);

foreach ($fruits as $key => $val) {  

  echo "$key = $val\\n";

}?>

The above example will output:

a = orange

b = banana

c = apple

d = lemon