uasort()

uasort() — Sort an array with a user-defined comparison function and maintain index association.

Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.

What it does

Sorts array in place such that its keys maintain their correlation with the values they are associated with, using a user-defined comparison function.

Signature

uasort(array &$array, callable $callback): true callback(mixed $a, mixed $b): int

Parameters

Parameter	Type	What it takes
&$array	array	The input array.
$callback	callable	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 value

Always returns true.

Example

A runnable snippet:

// 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);

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 )

Changelog

Version	Change
8.2.0	The return type is true now; previously, it was bool.
8.0.0	If callback expects a parameter to be passed by reference, this function will now emit an E_WARNING.