uasort
(PHP 4, PHP 5, PHP 7, PHP 8)
uasort — Sort an array with a user-defined comparison function and maintain index association
Description
uasort(array &$array, callable $callback): bool
Sorts array
in place such that its keys maintain their correlation with the values 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.
Note:
If two members compare as equal, they retain their original order. Prior to PHP 8.0.0, their relative order in the sorted array was undefined.
Note:
Resets array's internal pointer to the first element.
Parameters
-
array
-
The input array.
-
callback
-
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.
callback(mixed $a, mixed $b): int
Return Values
Always returns true
.
Changelog
Version | Description |
---|---|
8.0.0 | If callback expects a parameter to be passed by reference, this function will now emit an E_WARNING . |
Examples
Example #1 Basic uasort() example
<?php // Comparison function function cmp($a, $b) { if ($a == $b) { return 0; } return ($a < $b) ? -1 : 1; } // Array to be sorted $array = array('a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4); print_r($array); // Sort and print the resulting array uasort($array, 'cmp'); print_r($array); ?>
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
- usort() - Sort an array by values using a user-defined comparison function
- uksort() - Sort an array by keys using a user-defined comparison function
- The comparison of array sorting functions
© 1997–2021 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/function.uasort.php