PHP reference

usort

Sorts an array by a custom comparison rule.

Syntax

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

Parameters

Parameter	Type	Description
$array	array	The array being sorted.
$callback	callable	A function comparing two elements: returns a negative number, zero or a positive one.

Return value

trueAlways `true`; the array itself is modified.

Examples

Sorting by a field:

<?php
 
$users = [['name' => 'Oleg', 'age' => 31], ['name' => 'Anna', 'age' => 25]];
 
usort($users, fn ($a, $b) => $a['age'] <=> $b['age']);
 
echo implode(', ', array_column($users, 'name'));

Output:

Anna, Oleg

Descending order — the arguments are swapped:

<?php
 
$numbers = [3, 10, 1];
 
usort($numbers, fn ($a, $b) => $b <=> $a);
 
echo implode(', ', $numbers);

Output:

10, 3, 1

Notes

The keys are replaced with numbers from zero. To keep the keys, use uasort().

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.

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