Array Functions
PHP Manual

uasort

Sort an array with a user-defined comparison function and maintain index association

Description

bool uasort ( array &$array , callable $value_compare_func )

This function sorts an array such that array indices maintain their correlation with the array elements they are associated with, using a user-defined comparison function.

This is used mainly when sorting associative arrays where the actual element order is significant.

Note:

If two members compare as equal, their relative order in the sorted array is undefined.

Parameters

array

The input array.

value_compare_func

See usort and uksort for examples of user-defined comparison functions.

Return Values

Returns TRUE on success or FALSE on failure.

Examples

Example #1 Basic uasort example

<?php
// Comparison function
function cmp($a, $b) {
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

// Array to be sorted
$array = array('a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4);
print_r($array);

// Sort and print the resulting array
uasort($array, 'cmp');
print_r($array);
?>

The above example will output:

Array
(
    [a] => 4
    [b] => 8
    [c] => -1
    [d] => -9
    [e] => 2
    [f] => 5
    [g] => 3
    [h] => -4
)
Array
(
    [d] => -9
    [h] => -4
    [c] => -1
    [e] => 2
    [g] => 3
    [a] => 4
    [f] => 5
    [b] => 8
)