natcasesort

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

natcasesort — Sort an array using a case insensitive "natural order" algorithm

Description

natcasesort(array &$array): true

natcasesort() is a case insensitive version of natsort().

This function implements a sort algorithm that orders alphanumeric strings in the way a human being would while maintaining key/value associations. This is described as a "natural ordering".

Note:
If two members compare as equal, they retain their original order. Prior to PHP 8.0.0, their relative order in the sorted array was undefined.

Note:
Resets array's internal pointer to the first element.

Parameters

array: The input array.

Return Values

Always returns true.

Changelog

Version	Description
8.2.0	The return type is `true` now; previously, it was bool.

Examples

Example #1 natcasesort() example

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

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

natcasesort($array2);
echo "\nNatural order sorting (case-insensitive)\n";
print_r($array2);
?>

The above example will output:

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

Natural order sorting (case-insensitive)
Array
(
    [0] => IMG0.png
    [4] => img1.png
    [3] => img2.png
    [5] => IMG3.png
    [2] => img10.png
    [1] => img12.png
)

For more information see: Martin Pool's » Natural Order String Comparison page.

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User Contributed Notes 5 notes

down

dslicer at maine dot rr dot com ¶

21 years ago

Something that should probably be documented is the fact that both natsort and natcasesort maintain the key-value associations of the array. If you natsort a numerically indexed array, a for loop will not produce the sorted order; a foreach loop, however, will produce the sorted order, but the indices won't be in numeric order. If you want natsort and natcasesort to break the key-value associations, just use array_values on the sorted array, like so:

natcasesort($arr);
$arr = array_values($arr);

down

w-dot-rosenbach-at-netskill-de ¶

13 years ago

Sorting UTF-8 by arbitrary order:



<?php

mb_internal_encoding("UTF-8");



class utf_8_german

{

  // everything else is sorted at the end

  static $order = '0123456789AaÄäBbCcDdEeFfGgHhIiJjKkLlMm

NnOoÖöPpQqRrSsßTtUuÜüVvWwXxYyZz';

  static $char2order;

  

  static function cmp($a, $b) {

    if ($a == $b) {

        return 0;

    }

    

    // lazy init mapping

    if (empty(self::$char2order))

    {

      $order = 1;

      $len = mb_strlen(self::$order);

      for ($order=0; $order<$len; ++$order)

      {

        self::$char2order[mb_substr(self::$order, $order, 1)] = $order;

      }

    }

    

    $len_a = mb_strlen($a);

    $len_b = mb_strlen($b);

    $max=min($len_a, $len_b);

    for($i=0; $i<$max; ++$i)

    {

      $char_a= mb_substr($a, $i, 1);

      $char_b= mb_substr($b, $i, 1);

      

      if ($char_a == $char_b) continue;

      $order_a = (isset(self::$char2order[$char_a])) ? self::$char2order[$char_a] : 9999;

      $order_b = (isset(self::$char2order[$char_b])) ? self::$char2order[$char_b] : 9999;

      

      return ($order_a < $order_b) ? -1 : 1;

    }

    return ($len_a < $len_b) ? -1 : 1;

  }

}



// usage example:



$t = array(

  'Birnen', 'Birne', 'Äpfel', 'Apfel',

);



uasort($t, 'utf_8_german::cmp');

echo '$t: <pre>'.htmlspecialchars(print_r($t,true),null,'UTF-8').'</pre>';

?>

down

-1

claude at schlesser dot lu ¶

15 years ago

Here a function that will natural sort an array by keys with keys that contain special characters.



<?php

function natksort($array)

{

    $original_keys_arr = array();

    $original_values_arr = array();

    $clean_keys_arr = array();



    $i = 0;

    foreach ($array AS $key => $value)

    {

        $original_keys_arr[$i] = $key;

        $original_values_arr[$i] = $value;

        $clean_keys_arr[$i] = strtr($key, "ÄÖÜäöüÉÈÀËëéèàç", "AOUaouEEAEeeeac");

        $i++;

    }



    natcasesort($clean_keys_arr);



    $result_arr = array();



    foreach ($clean_keys_arr AS $key => $value)

    {

        $original_key = $original_keys_arr[$key];

        $original_value = $original_values_arr[$key];

        $result_arr[$original_key] = $original_value;

    }



    return $result_arr;

}

?>



Hope it will be useful to somebody :)

down

-1

vbAlexDOSMan at Yahoo dot com ¶

21 years ago

Ulli at Stemmeler dot net:  I remade your function -- it's a little more compact now -- Enjoy...

function ignorecasesort(&$array) {

  /*Make each element it's lowercase self plus itself*/
  /*(e.g. "MyWebSite" would become "mywebsiteMyWebSite"*/
  for ($i = 0; $i < sizeof($array); $array[$i] = strtolower($array[$i]).$array[$i], $i++);

  /*Sort it -- only the lowercase versions will be used*/
  sort($array);

  /*Take each array element, cut it in half, and add the latter half to a new array*/
  /*(e.g. "mywebsiteMyWebSite" would become "MyWebSite")*/
  for ($i = 0; $i < sizeof($array); $i++) {
    $this = $array[$i];
    $array[$i] = substr($this, (strlen($this)/2), strlen($this));
  }
}

down

-5

tmiller25 at hotmail dot com ¶

22 years ago

add this loop to the function above if you want items which have the same first characters to be listed in a way that the shorter string comes first.
--------------------
  /* short before longer (e.g. 'abc' should come before 'abcd') */
  for($i=count($array)-1;$i>0;$i--) {
    $str_a = $array[$i  ];
    $str_b = $array[$i-1];
    $cmp_a = strtolower(substr($str_a,0,strlen($str_a)));
    $cmp_b = strtolower(substr($str_b,0,strlen($str_a)));
    if ($cmp_a==$cmp_b && strlen($str_a)<strlen($str_b)) {
      $array[$i]=$str_b; $array[$i-1]=$str_a; $i+=2;
    }
  }
--------------------

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natcasesort

Description

Parameters

Return Values

Changelog

Examples

See Also

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User Contributed Notes 5 notes