PHP reference

uasort

Sorts an array by a custom rule, keeping the keys.

Syntax

uasort(array &$array, callable $callback): true

Parameters

Parameter	Type	Description
$array	array	The array being sorted.
$callback	callable	A function comparing two elements.

Return value

trueAlways `true`; the array itself is modified.

Examples

Sorting by a nested field while keeping the keys:

<?php
 
$users = [
    'oleg' => ['age' => 31],
    'anna' => ['age' => 25],
];
 
uasort($users, fn ($a, $b) => $a['age'] <=> $b['age']);
 
echo implode(', ', array_keys($users));

Output:

anna, oleg

Notes

usort() would replace the keys with numbers. uksort() sorts by key with a custom rule.

Related recipes

How to sort an array of arrays by a field

In the tutorial

Sorting arrays — Sorting in PHP — sort, rsort, asort, ksort, a custom rule with usort and the spaceship operator.

Thanks for reading!