(PHP 3 >= 3.0.4, PHP 4, PHP 5)

uksort --  Sort an array by keys using a user-defined comparison function


bool uksort ( array &array, callback cmp_function )

uksort() will sort the keys of an array using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.

Function cmp_function should accept two parameters which will be filled by pairs of array keys. The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

Returns TRUE on success or FALSE on failure.

Example 1. uksort() example

function cmp($a, $b)
    if (
$a == $b) {
    return (
$a > $b) ? -1 : 1;

$a = array(4 => "four", 3 => "three", 20 => "twenty", 10 => "ten");

uksort($a, "cmp");

foreach (
$a as $key => $value) {
"$key: $value\n";

The above example will output:

20: twenty
10: ten
4: four
3: three

See also usort(), uasort(), sort(), asort(), arsort(), ksort(), natsort(), and rsort().

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