krsort

bool krsort(array array, [int flag]) 

array	Array to be sorted
flag	Flag specifying how to compare key values (PHP 4.0.0+ only)

Sorts an array in descending order by key.

Returns:

TRUE on success; NULL on failure

Description:

This function sorts array in descending order by key. array is directly modified. (PHP 4.0.0+ only) The way in which element values are compared can be modified by passing one of the following named constants as flag :

SORT_REGULAR	Compare element keys according to PHP's normal comparison rules. This is the default if flag is not given.
SORT_NUMERIC	Compare element keys according to their numeric values.
SORT_STRING	Compare element keys according to their string values.

Version:

PHP 3 since 3.0.13, PHP 4 since 4.0b4

See also:

array_multisort() 
arsort() 
asort() 
ksort() 
natsort() 
natcasesort() 
rsort() 
sort() 
uasort() 
uksort() 
usort() 

Example:

Sort an array in reverse order by key

$array = array(2 => 1, '3' => 2, 1 => 3, 4 => 4); 
krsort($array); 
print_r($array); 

Output: 
Array 
(
    [4] => 4 
    [3] => 2 
    [2] => 1 
    [1] => 3 
)