Sort an array using a "natural order" algorithm

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Array Functions
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# natsort

(PHP 4, PHP 5)

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

### Description

bool natsort ( array `&$array` )

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.

### Parameters

`array`

  The input array.

### Return Values

Returns `TRUE` on success or `FALSE` on failure.

### Changelog

Version | Description
--- | ---
5.2.10 | Zero padded numeric strings (e.g., '00005') now essentially ignore the 0 padding.

### 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);
echo "Other characters interfering\n";
$images_oops = array('image_1.jpg','image_12.jpg', 'image_21.jpg', 'image_4.jpg');
print_r($images_oops);
natsort($images_oops);
print_r($images_oops);
echo "Sort by keys\n";
$smoothie = array('orange' => 1, 'apple' => 1, 'yogurt' => 4, 'banana' => 4);
print_r($smoothie);
uksort( $smoothie, 'strnatcmp');
print_r($smoothie);
?>`

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
    )

    Other characters interfering
    Array
    (
        [0] => image_1.jpg
        [1] => image_12.jpg
        [2] => image_21.jpg
        [3] => image_4.jpg
    )
    Array
    (
        [0] => image_1.jpg
        [3] => image_4.jpg
        [1] => image_12.jpg
        [2] => image_21.jpg
    )

    Sort by keys
    Array
    (
        [orange] => 1
        [apple]  => 1
        [yogurt] => 4
        [banana] => 4
    )
    Array
    (
        [apple]  => 1
        [banana] => 4
        [orange] => 1
        [yogurt] => 4
    )

### See Also

- natcasesort() - Sort an array using a case insensitive "natural order" algorithm
- The comparison of array sorting functions
- strnatcmp() - String comparisons using a "natural order" algorithm
- strnatcasecmp() - Case insensitive string comparisons using a "natural order" algorithm

natcasesort
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Array Functions
PHP Manual