PHP usort() Function

The PHP usort() function is used to sort an array using user-defined comparison function. The function must return an integer to work correctly and it should take only two parameters to compare.

Note: This function assigns new keys to the elements in array. It removes any existing keys that may have been assigned, rather than just reordering the keys.

Syntax

usort(array, myfunction)

Parameters

`array`	`Required.` Specify the input array to sort.
`myfunction`	`Required.` Specify user-defined function to compare values. The comparison function must return an integer <, =, or > than 0 if the first argument is <, =, or > than the second argument.

Return Value

Returns true on success and false in failure.

Exceptions

NA.

Example:

In the example below, usort() function is used to sort an array in ascending order using user-defined function.

<?php
//function to sort in ascending order
function MyFunc($x, $y) {
  if ($x == $y) 
    return 0;
  return ($x < $y)? -1: 1;
}

$Arr = array("Marry", "John", "Jo", "Kim", "Adam");
usort($Arr, "MyFunc");

print_r($Arr);
?>

The output of the above code will be:

Array
(
    [0] => Adam
    [1] => Jo
    [2] => John
    [3] => Kim
    [4] => Marry
)

Example:

Consider one more example where the function is defined to sort the array in descending order.

<?php
//function to sort in descending order
function MyFunc($x, $y) {
  if ($x == $y) 
    return 0;
  return ($x < $y)? 1: -1;
}

$Arr = array("Marry", "John", "Jo", "Kim", "Adam");
usort($Arr, "MyFunc");

print_r($Arr);
?>

The output of the above code will be:

Array
(
    [0] => Marry
    [1] => Kim
    [2] => John
    [3] => Jo
    [4] => Adam
)

❮ PHP Array Reference