natsort

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

natsort — "自然順"アルゴリズムで配列をソートする

説明

natsort(array &$array): true

この関数は、人間が行うような手法でアルファベットまたは数字の文字列の順番をキー/値の関係を保持したままソートします。これは、"自然順(natural ordering)"と呼ばれているものです。このアルゴリズムと (sort() を用いた) 通常のコンピュータ文字列ソートアルゴリズムの違いを示す例を以下に示します。

注意:
比較結果が等しくなる二つの要素があった場合、それらの並び順は保持されます。PHP 8.0.0 より前のバージョンでは、ソートした配列におけるそれらの並び順は不定でした。

注意:
この関数をコールすると、配列の内部ポインタは最初の要素にリセットされます。

パラメータ

array: 入力の配列。

戻り値

常に true を返します。

変更履歴

バージョン	説明
8.2.0	戻り値の型が、`true` になりました。これより前のバージョンでは、bool でした。

例

例1 natsort() の基本的な使用例

<?php
$array1 = $array2 = array("img12.png", "img10.png", "img2.png", "img1.png");

asort($array1);
echo "Standard sorting\n";
print_r($array1);

natsort($array2);
echo "\nNatural order sorting\n";
print_r($array2);
?>

上の例の出力は以下となります。

Standard sorting
Array
(
    [3] => img1.png
    [1] => img10.png
    [0] => img12.png
    [2] => img2.png
)

Natural order sorting
Array
(
    [3] => img1.png
    [2] => img2.png
    [1] => img10.png
    [0] => img12.png
)

より詳細な情報については、Martin Poolの » Natural Order String Comparison ページを参照ください。

例2 natsort() をより知るための例

<?php
echo "負の数\n";
$negative = array('-5','3','-2','0','-1000','9','1');
print_r($negative);
natsort($negative);
print_r($negative);

echo "ゼロ埋め\n";
$zeros = array('09', '8', '10', '009', '011', '0'); 
print_r($zeros);
natsort($zeros);
print_r($zeros);
?>

上の例の出力は以下となります。

負の数
Array
(
    [0] => -5
    [1] => 3
    [2] => -2
    [3] => 0
    [4] => -1000
    [5] => 9
    [6] => 1
)
Array
(
    [2] => -2
    [0] => -5
    [4] => -1000
    [3] => 0
    [6] => 1
    [1] => 3
    [5] => 9
)

ゼロ埋め
Array
(
    [0] => 09
    [1] => 8
    [2] => 10
    [3] => 009
    [4] => 011
    [5] => 0
)
Array
(
    [5] => 0
    [1] => 8
    [3] => 009
    [0] => 09
    [2] => 10
    [4] => 011
)

参考

natcasesort() - 大文字小文字を区別しない"自然順"アルゴリズムを用いて配列をソートする
配列ソート関数の比較
strnatcmp() - "自然順"アルゴリズムにより文字列比較を行う
strnatcasecmp() - "自然順"アルゴリズムにより大文字小文字を区別しない文字列比較を行う

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User Contributed Notes 19 notes

down

wyvern at greywyvern dot com ¶

16 years ago

There's no need to include your own API code to natsort an associative array by key.  PHP's in-built functions (other than natsort) can do the job just fine:

<?php
  uksort($myArray, "strnatcmp");
?>

down

Johan GENNESSON (php at genjo dot fr) ¶

14 years ago

Be careful of the new behaviour in 5.2.10 version.
See the following sample:

<?php

$array = array('1 bis', '10 ter', '0 PHP', '0', '01', '01 Ver', '0 ', '1 ', '1');

natsort($array);
echo '<pre>';
print_r($array);
echo '</pre>';
?>

5.2.6-1 will output:
Array
(
    [3] => 0
    [6] => 0 
    [2] => 0 OP
    [4] => 01
    [5] => 01 Ver
    [8] => 1
    [7] => 1 
    [0] => 1 bis
    [1] => 10 ter
)

5.2.10 will output:
Array
(
    [6] => 0 
    [3] => 0
    [8] => 1
    [4] => 01
    [7] => 1 
    [5] => 01 Ver
    [0] => 1 bis
    [1] => 10 ter
    [2] => 0 OP
)

Greetings

down

flash at minet dot net ¶

21 years ago

About the reverse natsort.. Maybe simpler to do :

function strrnatcmp ($a, $b) {
    return strnatcmp ($b, $a);
}

down

xlab AT adaptiveNOSPAMarts DOT net ¶

20 years ago

Under limited testing, natsort() appears to work well for IP addresses. For my needs, it is far less code than the ip2long()/long2ip() conversion I was using before.

down

rasmus at flajm dot com ¶

21 years ago

To make a reverse function, you can simply:

function rnatsort(&$a){
    natsort($a);
    $a = array_reverse($a, true);
}

down

mbirth at webwriters dot de ¶

20 years ago

For those who want to natsort a 2d-array on the first element of each sub-array, the following few lines should do the job.

<?php

function natsort2d(&$aryInput) {
  $aryTemp = $aryOut = array();
  foreach ($aryInput as $key=>$value) {
    reset($value);
    $aryTemp[$key]=current($value);
  }
  natsort($aryTemp);
  foreach ($aryTemp as $key=>$value) {
    $aryOut[] = $aryInput[$key];
  }
  $aryInput = $aryOut;
}

?>

down

anonymous at coward dot net ¶

21 years ago

Reverse Natsort:

  function rnatsort($a, $b) {
    return -1 * strnatcmp($a, $b);
  }

  usort($arr, "rnatsort");

down

ale152 ¶

15 years ago

Note: negatives number.
<?php
$a = array(-5,-2,3,9);
natsort($a);
print_r($a);
?>
Will output:
Array ( [1] => -2 [0] => -5 [2] => 3 [3] => 9 )

down

natcasesort.too ¶

19 years ago

I got caught out through naive use of this feature - attempting to sort a list of image filenames from a digital camera, where the filenames are leading zero padded (e.g. DSCF0120.jpg) , will not sort correctly.
Maybe the example could be modified to exhibit this behaviour 
(e.g. set array to -img0120.jpg','IMG0.png', 'img0012.png', 'img10.png', 'img2.png', 'img1.png', 'IMG3.png)
If the example hadn't used images I would have coded it correctly first time around!

down

phpnet at moritz-abraham dot de ¶

20 years ago

additional to the code posted by justin at redwiredesign dot com (which I found very usefull) here is a function that sorts complex arrays like this:
<?
$array['test0'] = array('main' =>  'a', 'sub' => 'a');
$array['test2'] = array('main' =>  'a', 'sub' => 'b');
$array['test3'] = array('main' =>  'b', 'sub' => 'c');
$array['test1'] = array('main' =>  'a', 'sub' => 'c');
$array['test4'] = array('main' =>  'b', 'sub' => 'a');
$array['test5'] = array('main' =>  'b', 'sub' => 'b');
?>
or
<?
$array[0] = array('main' =>  1, 'sub' => 1);
$array[2] = array('main' =>  1, 'sub' => 2);
$array[3] = array('main' =>  2, 'sub' => 3);
$array[1] = array('main' =>  1, 'sub' => 3);
$array[4] = array('main' =>  2, 'sub' => 1);
$array[5] = array('main' =>  2, 'sub' => 2);
?>
on one or more columns.

the code
<? $array = array_natsort_list($array,'main','sub'); ?>
will result in $array being sortet like this:
test0,test2,test1,test4,test5,test3
or
0,2,1,4,5,3.

you may even submit more values to the function as it uses a variable parameter list. the function starts sorting on the last and the goes on until the first sorting column is reached.

to me it was very usefull for sorting a menu having submenus and even sub-submenus.

i hope it might help you too.

here is the function:
<?
function array_natsort_list($array) {
    // for all arguments without the first starting at end of list
    for ($i=func_num_args();$i>1;$i--) {
        // get column to sort by
        $sort_by = func_get_arg($i-1);
        // clear arrays
        $new_array = array();
        $temporary_array = array();
        // walk through original array
        foreach($array as $original_key => $original_value) {
            // and save only values
            $temporary_array[] = $original_value[$sort_by];
        }
        // sort array on values
        natsort($temporary_array);
        // delete double values
        $temporary_array = array_unique($temporary_array);
        // walk through temporary array
        foreach($temporary_array as $temporary_value) {
            // walk through original array
            foreach($array as $original_key => $original_value) {
                // and search for entries having the right value
                if($temporary_value == $original_value[$sort_by]) {
                    // save in new array
                    $new_array[$original_key] = $original_value;
                }
            }
        }
        // update original array
        $array = $new_array;
    }
    return $array;
}
?>

down

bb7b5b9 at gmail dot com ¶

8 years ago

This made me waste a lot of my precious youth ... natsort() is buggy if all numbers don't have the same number of decimal places.

(php 5.6.4-4ubuntu6.2)

<?php 
$different_decimal_places_in_values = array('D'=>'13.59', '14.6' => '14.6', 'C-' => '14.19'); 
natsort($a); 
var_dump($a);

/*echoes
array(3) {
  'D' =>
  string(5) "13.59"
  '14.6' =>
  string(4) "14.6" <----------- badly ordered
  'C-' =>
  string(5) "14.19"
}*/
?>

While this 

<?php 
$same_num_decimal_places_in_values = array('D'=>'13.59', '14.6' => '14.60', 'C-' => '14.19'); natsort($a); var_dump($a);

/*echoes 
array(3) {
  'D' =>
  string(5) "13.59"
  'C-' =>
  string(5) "14.19"
  '14.6' =>
  string(5) "14.60" <--------- that is the correct position
}
*/

?>

down

lacent at gmail dot com ¶

17 years ago

there is another rnatsort function lower on the page, but it didn't work in the context i needed it in. 

reasoning for this:
sorting naturally via the keys of an array, but needing to reverse the order.

    function rnatsort ( &$array = array() ) 
    {
        $keys    = array_keys($array);
        natsort($keys);
        $total    = count($keys) - 1;
        $temp1    = array();
        $temp2     = array();

        // assigning original keys to an array with a backwards set of keys, to use in krsort();
        foreach ( $keys as $key )
        {
            $temp1[$total] = $key;
            --$total;
        }
        
        ksort($temp1);

        // setting the new array, with the order from the krsort() and the values of original array.
        foreach ( $temp1 as $key ) 
        {
            $temp2[$key] = $array[$key];
        }

        $array = $temp2;
    }

down

h3 ¶

18 years ago

This function can be very usefull, but in some cases, like if you want to sort a MySQL query result, it's important to keep in mind that MySQL as built'in sorting functions which are way faster than resorting the result using a complex php algorythm, especially with large arrays.

ex; 'SELECT * FROM `table` ORDER BY columnName ASC, columnName2 DESC'

down

Malek Mohamed ¶

6 years ago

$array1 = $array2 = array('IMG0.png', 'img12.png', 'img10.png', 'img2.png', 'img1.png', 'IMG3.png');

natsort($array1);
echo "\n natsort(); \n";
print_r($array1);

sort($array2, SORT_NATURAL);
echo "\n sort() with  SORT_NATURAL Option\n";
print_r($array2);

Ouput:

natsort();
Array
(
    [0] => IMG0.png
    [5] => IMG3.png
    [4] => img1.png
    [3] => img2.png
    [2] => img10.png
    [1] => img12.png
)

sort() with  SORT_NATURAL Option
Array
(
    [0] => IMG0.png
    [1] => IMG3.png
    [2] => img1.png
    [3] => img2.png
    [4] => img10.png
    [5] => img12.png
)

as we can see it's  the same values but not the same keys, and also it's same for sort($array1, SORT_NATURAL | SORT_FLAG_CASE); and natcasesort($array2)

down

dotancohen splat gmail spot com ¶

7 years ago

As noted in other notes, natsort() does _not_ always return the expected sort order. It seems especially buggy when decimals or 0 padding is used. I've filed this bug report on the issue:
https://bugs.php.net/bug.php?id=74672

down

mvs dot php at gmail dot com ¶

9 years ago

To naturally sort by array key, the uksort function can be used.

<?php

echo "Sort by keys\n";
$smoothie = array('orange' => 1, 'apple' => 1, 'yogurt' => 4, 'banana' => 4);
print_r($smoothie);
uksort( $smoothie, 'strnatcmp');
print_r($smoothie)

?>

Output:

Sort by keys
Array
(
    [orange] => 1
    [apple]  => 1
    [yogurt] => 4
    [banana] => 4
)
Array
(
    [apple]  => 1
    [banana] => 4
    [orange] => 1
    [yogurt] => 4
)

See http://php.net/manual/en/function.uksort.php for more information about uksort and http://php.net/strnatcmp for usage of strnatcmp.

down

@gmail bereikme ¶

18 years ago

Here's a handy function to sort an array on 1 or more columns using natural sort:
<?php
// Example: $records = columnSort($records, array('name', 'asc', 'addres', 'desc', 'city', 'asc'));

$globalMultisortVar = array();
function columnSort($recs, $cols) {
    global $globalMultisortVar;
    $globalMultisortVar = $cols;
    usort($recs, 'multiStrnatcmp');
    return($recs);
}

function multiStrnatcmp($a, $b) {
    global $globalMultisortVar;
    $cols = $globalMultisortVar;
    $i = 0;
    $result = 0;
    while ($result == 0 && $i < count($cols)) {
        $result = ($cols[$i + 1] == 'desc' ? strnatcmp($b[$cols[$i]], $a[$cols[$i]]) : $result = strnatcmp($a[$cols[$i]], $b[$cols[$i]]));
        $i+=2;
    }
    return $result;
}

?>

Greetings,

  - John

down

-1

lil at thedreamersmaze dot spam-me-not dot org ¶

18 years ago

There's one little thing missing in this useful bit of code posted by mbirth at webwriters dot de:

<?php

function natsort2d(&$aryInput) {
  $aryTemp = $aryOut = array();
  foreach ($aryInput as $key=>$value) {
   reset($value);
   $aryTemp[$key]=current($value);
  }
  natsort($aryTemp);
  foreach ($aryTemp as $key=>$value) {
   $aryOut[$key] = $aryInput[$key]; 
// --------^^^^ add this if you want your keys preserved!
  }
  $aryInput = $aryOut;
}

?>

down

-4

AJenbo ¶

15 years ago

natsort might not act like you would expect with zero padding, heres a quick sample.



<?php

$array = array('09', '8', '10', '009', '011');

natsort($array);

?>

/*

Array

(

    [3] => 009

    [4] => 011

    [0] => 09

    [1] => 8

    [2] => 10

)

*/

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