PHP Manual
Array Functions
Sort an array using a "natural order" algorithm

natsort

(PHP 4, PHP 5, PHP 7, PHP 8)

natsort — Sort an array using a "natural order" algorithm

Description

natsort(array &$array): bool

This function implements a sort algorithm that orders alphanumeric strings in the way a human being would while maintaining key/value associations. This is described as a "natural ordering". An example of the difference between this algorithm and the regular computer string sorting algorithms (used in sort()) can be seen in the example below.

Note:
If two members compare as equal, they retain their original order. Prior to PHP 8.0.0, their relative order in the sorted array was undefined.

Note:
Resets array's internal pointer to the first element.

Parameters

array: The input array.

Return Values

Always returns true.

Examples

Example #1 natsort() examples demonstrating basic usage


<?php
$array1 = $array2 = array("img12.png", "img10.png", "img2.png", "img1.png");

asort($array1);
echo "Standard sorting\n";
print_r($array1);

natsort($array2);
echo "\nNatural order sorting\n";
print_r($array2);
?>

The above example will output:

Standard sorting
Array
(
    [3] => img1.png
    [1] => img10.png
    [0] => img12.png
    [2] => img2.png
)

Natural order sorting
Array
(
    [3] => img1.png
    [2] => img2.png
    [1] => img10.png
    [0] => img12.png
)

For more information see: Martin Pool's » Natural Order String Comparison page.

Example #2 natsort() examples demonstrating potential gotchas


<?php
echo "Negative numbers\n";
$negative = array('-5','3','-2','0','-1000','9','1');
print_r($negative);
natsort($negative);
print_r($negative);

echo "Zero padding\n";
$zeros = array('09', '8', '10', '009', '011', '0'); 
print_r($zeros);
natsort($zeros);
print_r($zeros);
?>

The above example will output:

Negative numbers
Array
(
    [0] => -5
    [1] => 3
    [2] => -2
    [3] => 0
    [4] => -1000
    [5] => 9
    [6] => 1
)
Array
(
    [2] => -2
    [0] => -5
    [4] => -1000
    [3] => 0
    [6] => 1
    [1] => 3
    [5] => 9
)

Zero padding
Array
(
    [0] => 09
    [1] => 8
    [2] => 10
    [3] => 009
    [4] => 011
    [5] => 0
)
Array
(
    [5] => 0
    [1] => 8
    [3] => 009
    [0] => 09
    [2] => 10
    [4] => 011
)