usort

Name:usort

Category:Array

Programming Language:php

One-line Description:Sort arrays using user-defined comparison functions.

Definition and usage

usort() sorts the array through a user-defined comparison function.

Example

Use a user-defined comparison function to sort elements in 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" ) ;
?>

Try it yourself

grammar

 usort ( array , myfunction ) ;

parameter	describe
array	Required. Specifies the array to be sorted.
myfunction	Optional. Defines a string that calls the comparison function. If the first parameter is less than or greater than the second parameter, the comparison function must return an integer less than or greater than 0.

illustrate

usort() function uses user-defined functions to sort arrays.

Note: If the comparison results of two elements are the same, the order in which they are in the sorted array is undefined. Until PHP 4.0.6, user-defined functions retain the original order of these elements. However, due to the introduction of a new sorting algorithm in 4.1.0, the result will not be this because there is no effective solution to this.

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