PHP usort() Function
Topic: PHP Array ReferencePrev|Next
Description
The usort() function sorts an array by values using a user-defined comparison function.
The following table summarizes the technical details of this function.
| Return Value: | Returns TRUE on success or FALSE on failure. |
|---|---|
| Version: | PHP 4+ |
Syntax
The basic syntax of the usort() function is given with:
The following example shows the usort() function in action.
Example
Run this code »<?php
// Define comparison function
function compare($a, $b){
if($a == $b){
return 0;
}
return ($a < $b) ? -1 : 1;
}
// Sample array
$numbers = array(2, 5, 4, 3, 6, 1);
// Sort numbers array using compare function
usort($numbers, "compare");
print_r($numbers);
?>Note: The comparison function must return an integer equal to zero if both values are equal, an integer less than zero if the first value is less than the second value, and an integer greater than zero if the first value is greater than the second value.
Tip: The usort() function assigns new keys to the elements in array. It will remove any existing keys that may have been assigned, rather than just reordering the keys.
Parameters
The usort() function accepts the following parameters.
| Parameter | Description |
|---|---|
| array | Required. Specifies the array to be sorted. |
| compare_function | Optional. Specifies the compare function to use for sorting. |
