String comparisons using a "natural order" algorithm

strnatcasecmp
strncasecmp
String Functions
PHP Manual

# 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". Note that this comparison is case sensitive.

### Parameters

`str1`

  The first string.

`str2`

  The second string.

### Return Values

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.

### Examples

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 above example will 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.

### See Also

- preg_match() - Perform a regular expression match
- strcasecmp() - Binary safe case-insensitive string comparison
- substr() - Return part of a string
- stristr() - Case-insensitive strstr
- strcmp() - Binary safe string comparison
- strncmp() - Binary safe string comparison of the first n characters
- strncasecmp() - Binary safe case-insensitive string comparison of the first n characters
- strnatcasecmp() - Case insensitive string comparisons using a "natural order" algorithm
- strstr() - Find the first occurrence of a string
- natsort() - Sort an array using a "natural order" algorithm
- natcasesort() - Sort an array using a case insensitive "natural order" algorithm

strnatcasecmp
strncasecmp
String Functions
PHP Manual