strnatcmp

String comparisons using a "natural order" algorithm (PHP 4, PHP 5)
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:

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<?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:

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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()

strcasecmp()

substr()

stristr()

strcmp()

strncmp()

strncasecmp()

strnatcasecmp()

strstr()

natsort()

natcasesort()

There seems to be a bug in the localization for strnatcmp and strnatcasecmp. I searched the reported bugs and found a few entries which were up to four years old (but the problem still exists when using swedish characters). These functions might work instead. <?php function _strnatcasecmp($left, $right) { return _strnatcmp(strtolower($left), strtolower($right)); } function _strnatcmp($left, $right) { while((strlen($left) > 0) && (strlen($right) > 0)) { if(preg_match('/^([^0-9]*)([0-9].*)$/Us', $left, $lMatch)) { $lTest = $lMatch[1]; $left = $lMatch[2]; } else { $lTest = $left; $left = ''; } if(preg_match('/^([^0-9]*)([0-9].*)$/Us', $right, $rMatch)) { $rTest = $rMatch[1]; $right = $rMatch[2]; } else { $rTest = $right; $right = ''; } $test = strcmp($lTest, $rTest); if($test != 0) { return $test; } if(preg_match('/^([0-9]+)([^0-9].*)?$/Us', $left, $lMatch)) { $lTest = intval($lMatch[1]); $left = $lMatch[2]; } else { $lTest = 0; } if(preg_match('/^([0-9]+)([^0-9].*)?$/Us', $right, $rMatch)) { $rTest = intval($rMatch[1]); $right = $rMatch[2]; } else { $rTest = 0; } $test = $lTest - $rTest; if($test != 0) { return $test; } } return strcmp($left, $right); } ?> The code is not optimized. It was just made to solve my problem.

strnatcmp

String comparisons using a "natural order" algorithm (PHP 4, PHP 5)
int strnatcmp ( string str1, string str2 )

Parameters

Return Values

Examples

Code Examples / Notes » strnatcmp

Change Language

strnatcmp

String comparisons using a "natural order" algorithm (PHP 4, PHP 5) int strnatcmp ( string str1, string str2 )

Parameters

Return Values

Examples

Code Examples / Notes » strnatcmp

Change Language

String comparisons using a "natural order" algorithm (PHP 4, PHP 5)
int strnatcmp ( string str1, string str2 )