PHP: strnatcmp

Description

int strnatcmp ( string str1, string str2 )

This function implements a comparison algorithm that orders alphanumeric strings in the way a human being would, this is described as a "natural ordering". An example of the difference between this algorithm and the regular computer string sorting algorithms (used in strcmp()) can be seen below:


<?php

$arr1 = $arr2 = array("img12.png", "img10.png", "img2.png", "img1.png");

echo "Standard string comparison\n";

usort($arr1, "strcmp");

print_r($arr1);

echo "\nNatural order string comparison\n";

usort($arr2, "strnatcmp");

print_r($arr2);

?>

The code above will generate the following output:

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

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

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

Similar to other string comparison functions, this one returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal.

Note that this comparison is case sensitive.

User Contributed Notes
strnatcmp

public at macfreek dot nl
15-Aug-2002 09:03


The URI of Martin Pool's page is http://sourcefrog.net/projects/natsort/

(Yes, that's frog, not forge).



http://www.naturalordersort.org/ points to a page with the same idea, by Stuart Cheshire, who wrote a small Mac extension to do natural sorting.

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