strnatcmp()

strnatcmp() — String comparisons using a "natural order" algorithm.

Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.

What it does

This function implements a comparison algorithm that orders alphanumeric strings in the way a human being would, this is described as a "natural ordering". Note that this comparison is case sensitive.

Signature

strnatcmp(string $string1, string $string2): int

Parameters

Parameter	Type	What it takes
$string1	string	The first string.
$string2	string	The second string.

Return value

Returns a value less than 0 if string1 is less than string2; a value greater than 0 if string1 is greater than string2, and 0 if they are equal. No particular meaning can be reliably inferred from the value aside from its sign.

Example

A runnable snippet:

$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);

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 )

Changelog

Version	Change
8.2.0	This function is no longer guaranteed to return strlen($string1) - strlen($string2) when string lengths are not equal, but may now return -1 or 1 instead.