PHP 8 reference · Array Sorting Functions

PHP ksort() Function

Sort an array by key in ascending order, keeping each value with its key.

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Syntax

ksort(array &$array, int $flags = SORT_REGULAR): true

Parameter	Description
`array`	The array to sort (changed in place).
`flags` optional	`SORT_REGULAR`, `SORT_NUMERIC`, `SORT_STRING`, `SORT_NATURAL`, optionally `\| SORT_FLAG_CASE`. Default: `SORT_REGULAR`

Always true.

Sort by keyTry it yourself

<?php
$config = ["timeout" => 30, "debug" => false, "name" => "app"];
ksort($config);
print_r($config);

Output

Array
(
    [debug] => 
    [name] => app
    [timeout] => 30
)

Numeric keysTry it yourself

<?php
$byYear = [2026 => "now", 1999 => "then", 2010 => "between"];
ksort($byYear);
echo implode(", ", $byYear), "\n";

Output

then, between, now

Version	Change
PHP 4.0	Added
PHP 8.0	Sorting is stable: elements that compare equal keep their original order.
PHP 8.2	The return type is `true` (it was `bool`).

krsort() · Sort an array by key in descending order, keeping each value with its key.
uksort() · Sort an array by key with your own comparison function, keeping values with their keys.
asort() · Sort an array by value in ascending order, keeping each key attached to its value. Ideal for name => score maps.
sort() · Sort an array's values in ascending order, in place. Keys are discarded and the result is renumbered from 0.
PHP Arrays · tutorial
PHP Array Functions · tutorial