Sort the entries with a user-defined comparison function and maintain key association

ArrayObject::setIteratorClass
ArrayObject::uksort
ArrayObject
PHP Manual

# ArrayObject::uasort

(PHP 5 >= 5.2.0)

ArrayObject::uasort — Sort the entries with a user-defined comparison function and maintain key association

### Description

public void ArrayObject::uasort ( callable `$cmp_function` )

This function sorts the entries such that keys maintain their correlation with the entry that 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.

### Parameters

`cmp_function`

  Function `cmp_function` should accept two parameters which will be filled by pairs of entries. 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.

### Return Values

No value is returned.

### Examples

Example #1 ArrayObject::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);
$arrayObject = new ArrayObject($array);
print_r($arrayObject);
// Sort and print the resulting array
$arrayObject->uasort('cmp');
print_r($arrayObject);
?>`

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
    )

### See Also

- ArrayObject::asort() - Sort the entries by value
- ArrayObject::ksort() - Sort the entries by key
- ArrayObject::natsort() - Sort entries using a "natural order" algorithm
- ArrayObject::natcasesort() - Sort an array using a case insensitive "natural order" algorithm
- ArrayObject::uksort() - Sort the entries by keys using a user-defined comparison function

ArrayObject::setIteratorClass
ArrayObject::uksort
ArrayObject
PHP Manual