strnatcmp

(PHP 4, PHP 5, PHP 7, PHP 8)

strnatcmp — String comparisons using a "natural order" algorithm

Descrição

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

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.

Parâmetros

string1: The first string.
string2: The second string.

Valor Retornado

Similar to other string comparison functions, this one returns -1 if string1 is less than string2; 1 if string1 is greater than string2, and 0 if they are equal.

Registro de Alterações

Versão	Descrição
8.2.0	Esta função agora retorna `-1` ou `1`, onde anteriormente retornava um número negativo ou positivo.

Exemplos

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);
?>

O exemplo acima produzirá:

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.

Veja Também

preg_match() - Perform a regular expression match
strcasecmp() - Binary safe case-insensitive string comparison
substr() - Retorna parte de uma string
stristr() - Case-insensitive strstr
strcmp() - Binary safe string comparison
strncmp() - Binary safe string comparison of the first n characters
strncasecmp() - Comparação binária de strings, insensível a maiúsculas/minúsculas, dos primeiros n caracteres
strnatcasecmp() - Comparação de strings insensível a maiúsculas/minúsculas usando o algoritmo de "ordem natural"
strstr() - Find the first occurrence of a string
natsort() - Ordena um array utilizando o algoritmo de "ordem natural"
natcasesort() - Ordena um array utilizando o algoritmo da "ordem natural" sem diferenciar maiúsculas e minúsculas

add a note

User Contributed Notes 4 notes

down

in dot games dot mq at gmail dot com ¶

7 years ago


Can also be used with combination of a compare for an array nested value, like

<?php
$array = array(
    "city" => "xyz",
    "names" => array(
        array(
            "name" => "Ana2",
            "id" => 1
        ) ,
        array(
            "name" => "Ana1",
            "id" => 2
        )
    )
);
usort($array["names"], function ($a, $b)    {    return strnatcmp($a['name'], $b['name']);} );

down

thomas at uninet dot se ¶

18 years ago


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.

down

-1

chris at ocproducts dot com ¶

7 years ago


This function has some interesting behaviour on strings consisting of mixed numbers and letters.

One may expect that such a mixed string would be treated as alpha-numeric, but that is not true.

var_dump(strnatcmp('23','123')); →
int(-1)
As expected, 23<123   (even though first digit is higher, overall number is smaller)

var_dump(strnatcmp('yz','xyz')); →
int(1)
As expected, yz>xyz   (string comparison, irregardless of string length)

var_dump(strnatcmp('2x','12y')); →
int(-1)
Remarkable, 2x<12y    (does a numeric comparison)

var_dump(strnatcmp('20x','12y'));
int(1)
Remarkable, 20x>12y    (does a numeric comparison)

It seems to be splitting what is being compared into runs of numbers and letters, and then comparing each run in isolation, until it has an ordering difference.

down

-4

spamspamspam at gmx dot com ¶

6 years ago


Some more remarkable outcomes:

var_dump(strnatcmp("0.15m", "0.2m"));
int(1)

var_dump(strnatcmp("0.15m", "0.20m"));
int(-1)

It's not about localisation:

var_dump(strnatcmp("0,15m", "0,2m"));
int(1)

var_dump(strnatcmp("0,15m", "0,20m"));
int(-1)

add a note