PHP usort( ) function

The PHP usort( ) function is used to sort an array by its value using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function. This function was introduced in PHP 4.0.

Syntax

Parameter

Parameter	Description	Is compulsory
array	Specifies the array to be sorted.	compulsory
user_defined_function	This function is a comparison function and it is used to compare values and sort the array. This function returns three types of values. If a=b, return 0 If a>b, return 1 If a<b, return -1	Optional

Return type

The usort( ) function returns true on success and false on failure.

Example 1

<?php
function  compare($a, $b) 
{
if ($a == $b) return 0;
return ($a > $b) ? -1 : 1;
}
$country = array("d"=>"denmark", "a"=>"australia", "b"=>"bangladesh" );
usort($country, "compare");
print_r($country);
?>

Output:

Array
(
    [0] => denmark
    [1] => bangladesh
    [2] => australia
)

Example 2

<?php
function   mysort($a,$b)
{
if ($a==$b) return 0;
return ($a<$b)?-1:1;
}
$numbers=array(11,56,8,96);
usort($numbers,"mysort");
print_r($numbers)
?>

Output:

Array
(
    [0] => 8
    [1] => 11
    [2] => 56
    [3] => 96
)

Example 3

<?php
function   myfunction($a,$b)
{
if ($a==$b) return 0;
return ($a<$b)?-1:1;
}
$language=array('php','java','c++','csharp');
usort($language,"myfunction");
print_r($language);
?>

Output:

Array
(
    [0] => c++
    [1] => csharp
    [2] => java
    [3] => php
)

Example 4

<?php
function  userdefined($a,$b)
{
if ($a==$b) return 0;
return ($a<$b)?-1:1;
}
$news=array('aajtak','abp','zee news','ndtv');
usort($news,"userdefined");
print_r($news);
?>

Output:

Array
(
    [0] => aajtak
    [1] => abp
    [2] => ndtv
    [3] => zee news
)

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