PHP Manual: strnatcmp

strnatcmp

(PHP 4, PHP 5)

strnatcmp -- String comparisons using a "natural order" algorithm

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.