How to use the php usort() function

PHP usort() function

Example

Using user The custom comparison function sorts the elements in the array $a:

<?php
function my_sort($a,$b)
{
if ($a==$b) return 0;
return ($a<$b)?-1:1;
}

$a=array(4,2,8,6);usort($a,"my_sort");
?>

Definition and usage

usort() is user-defined The comparison function sorts the array.

Syntax

usort(array,myfunction);

Parameters	Description
array	Required. Specifies the array to be sorted.
myfunction	Optional. Defines a string on which a comparison function can be called. If the first argument is less than or equal to or greater than the second argument, the comparison function must return an integer less than or equal to or greater than 0.

Description

The usort() function uses a user-defined function to sort the array.

Comments: If the comparison results of two elements are the same, their order in the sorted array is undefined. Prior to PHP 4.0.6, user-defined functions would preserve the original order of these elements. But due to the new sorting algorithm introduced in 4.1.0, this will no longer be the case as there is no efficient solution for this.

Comments: This function assigns new key names to elements in array. This will delete the original key name.

Technical details

Return value:	Returns TRUE if successful, If failed, return FALSE.
PHP version:	4

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