Sort php array by key

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

ksort — Sort an array by key in ascending order

Description

ksort(array &$array, int $flags = SORT_REGULAR): bool

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

The input array.

The optional second parameter flags may be used to modify the sorting behavior using these values:

Sorting type flags:

• SORT_REGULAR - compare items normally; the details are described in the comparison operators section
• SORT_NUMERIC - compare items numerically
• SORT_STRING - compare items as strings
• SORT_LOCALE_STRING - compare items as strings, based on the current locale. It uses the locale, which can be changed using setlocale()
• SORT_NATURAL - compare items as strings using "natural ordering" like natsort()
• SORT_FLAG_CASE - can be combined (bitwise OR) with SORT_STRING or SORT_NATURAL to sort strings case-insensitively

Return Values

Always returns true.

Examples

Example #1 ksort() example

$fruits = array("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
ksort($fruits);
foreach ($fruits as $key => $val) {
    echo "$key = $val\n";
}
?>

The above example will output:

a = orange
b = banana
c = apple
d = lemon

Example #2 ksort() with int keys

$a = [0 => 'First', 2 => 'Last', 1 => 'Middle'];
var_dump($a);
ksort($a);
var_dump($a);
?>

The above example will output:

array(3) {
  [0]=>
  string(5) "First"
  [2]=>
  string(4) "Last"
  [1]=>
  string(6) "Middle"
}
array(3) {
  [0]=>
  string(5) "First"
  [1]=>
  string(6) "Middle"
  [2]=>
  string(4) "Last"
}

See Also

• sort() - Sort an array in ascending order
• krsort() - Sort an array by key in descending order
• The comparison of array sorting functions

DavidG ¶

12 years ago

A nice way to do sorting of a key on a multi-dimensional array without having to know what keys you have in the array first:

$people = array(
array("name"=>"Bob","age"=>8,"colour"=>"red"),
array("name"=>"Greg","age"=>12,"colour"=>"blue"),
array("name"=>"Andy","age"=>5,"colour"=>"purple")); var_dump($people); $sortArray = array();

foreach(

orlov0562 at gmail dot com ¶

5 years ago

The first thing that I didn't find in description it's that this function return results from MIN value to MAX value, ex: [-5=>'', 0=>'', 5=>'' ]

Also you should know that by default, it has correct sorting for keys that represented as string but has a number as value, ex: ['-5'=>'', '0'=>'', '5'=>'' ]

Few examples with results:

-----------------------------------------

DESCRIPTION: Keys are numbers + default flag (SORT_REGULAR)

$arr = [
    -5 => 'minus five',
    0 => 'zero',
    1 => 'one',
    2 => 'two',
    100 => 'hundred',
];

ksort($arr);
print_r($arr);

RESULT:

Array
(
    [-5] => minus five
    [0] => zero
    [1] => one
    [2] => two
    [100] => hundred
)

-----------------------------------------
DESCRIPTION: Keys are string numbers + default flag (SORT_REGULAR)

$arr = [
    '-5' => 'minus five',
    '0' => 'zero',
    '1' => 'one',
    '2' => 'two',
    '100' => 'hundred',
];

ksort($arr);
print_r($arr);

RESULT:

Array
(
    [-5] => minus five
    [0] => zero
    [1] => one
    [2] => two
    [100] => hundred
)

-----------------------------------------
DESCRIPTION: Keys are string numbers + SORT_STRING flag

$arr = [
    '-5' => 'minus five',
    '0' => 'zero',
    '1' => 'one',
    '2' => 'two',
    '100' => 'hundred',
];

ksort($arr, SORT_STRING);
print_r($arr);

RESULT:

Array
(
    [-5] => minus five
    [0] => zero
    [1] => one
    [100] => hundred
    [2] => two
)

-----------------------------------------

DESCRIPTION: Keys are string numbers + SORT_NUMERIC flag

$arr = [
    '-5' => 'minus five',
    '0' => 'zero',
    '1' => 'one',
    '2' => 'two',
    '100' => 'hundred',
];

ksort($arr, SORT_NUMERIC);
print_r($arr);

RESULT:

Array
(
    [-5] => minus five
    [0] => zero
    [1] => one
    [2] => two
    [100] => hundred
)

thegrandoverseer ¶

10 years ago

I wrote this function to sort the keys of an array using an array of keynames, in order.
/**
* function array_reorder_keys
* reorder the keys of an array in order of specified keynames; all other nodes not in $keynames will come after last $keyname, in normal array order
* @param array &$array - the array to reorder
* @param mixed $keynames - a csv or array of keynames, in the order that keys should be reordered
*/
function array_reorder_keys(&$array, $keynames){
    if(empty($array) || !is_array($array) || empty($keynames)) return;
    if(!is_array($keynames)) $keynames = explode(',',$keynames);
    if(!empty($keynames)) $keynames = array_reverse($keynames);
    foreach($keynames as $n){
        if(array_key_exists($n, $array)){
            $newarray = array($n=>$array[$n]); //copy the node before unsetting
            unset($array[$n]); //remove the node
            $array = $newarray + array_filter($array); //combine copy with filtered array
        }
    }
}
$seed_array = array('foo'=>'bar', 'someotherkey'=>'whatev', 'bar'=>'baz', 'baz'=>'foo', 'anotherkey'=>'anotherval');
array_reorder_keys($seed_array, 'baz,foo,bar'); //returns array('baz'=>'foo', 'foo'=>'bar', 'bar'=>'baz', 'someotherkey'=>'whatev', 'anotherkey'=>'anotherval' );
?>

Anonymous ¶

20 years ago

here 2 functions to ksort/uksort an array and all its member arrays

function tksort(&$array)
  {
  ksort($array);
  foreach(array_keys($array) as $k)
    {
    if(gettype($array[$k])=="array")
      {
      tksort($array[$k]);
      }
    }
  }

function utksort(&$array, $function)
  {
  uksort($array, $function);
  foreach(array_keys($array) as $k)
    {
    if(gettype($array[$k])=="array")
      {
      utksort($array[$k], $function);
      }
    }
  }

ssb45 at cornell dot edu ¶

17 years ago

The function that justin at booleangate dot org provides works well, but be aware that it is not a drop-in replacement for ksort as is.  While ksort sorts the array by reference and returns a status boolean, natksort returns the sorted array, leaving the original untouched.  Thus, you must use this syntax:

$array = natksort($array);

If you want to use the more natural syntax:

$status = natksort($array);

Then use this modified version:

function natksort(&$array) {
    $keys = array_keys($array);
    natcasesort($keys);

    foreach ($keys as $k) {
        $new_array[$k] = $array[$k];
    }

    $array = $new_array;
    return true;
}

serpro at gmail dot com ¶

13 years ago

Here is a function to sort an array by the key of his sub-array.

function sksort(&$array, $subkey="id", $sort_ascending=false) {

    if (

bimal at sanjaal dot com ¶

8 years ago

An example of reverse sorting a domain name by its name.

$domains = array(
    'sub.domain.com',
    'sub2.domain.com',
);

foreach(

sbarnum at mac dot com ¶

20 years ago

ksort on an array with negative integers as keys yields some odd results.  Not sure if this is a bad idea (negative key values) or what.

Anonymous ¶

9 years ago

Note that this function will output the given $fields in the order they were added to the data array and not automatically in numerical key order.

To output in ascending key order, you'll need to ksort the array first (or use appropriate natural order sorting, depending on your keys).

For example:
$data[2] = 'C';
$data[0] = 'A';
$data[1] = 'B';fputcsv($fh, $data); // outputs: "C,A,B"ksort($data);
fputcsv($fh, $data); // outputs: "A,B,C"
?>

delvach at mail dot com ¶

20 years ago

A real quick way to do a case-insensitive sort of an array keyed by strings:

uksort($myArray, "strnatcasecmp");

justin at booleangate dot org ¶

17 years ago

Here's a handy function for natural order sorting on keys.

function natksort($array) {
  // Like ksort but uses natural sort instead
  $keys = array_keys($array);
  natsort($keys);

  foreach ($keys as $k)
    $new_array[$k] = $array[$k];

  return $new_array;
}

Anonymous ¶

8 years ago

@thegrandoverseer 

you could also use the build-in php array functions to get exactly what you want to have:

        $seed_array = array('foo'=>'bar', 'someotherkey'=>'whatev', 'bar'=>'baz', 'baz'=>'foo', 'anotherkey'=>'anotherval');
        $keys_array = array('baz', 'foo', 'bar');$return_array = array_intersect_key($seed_array, array_flip($keys_array)) + array_diff_key($seed_array, array_flip($keys_array));?>

stephen [ at ] brooksie-net [ dot ] co [ dot ] uk ¶

9 years ago

ksort and krsort fail to undestand scientific notation, https://bugs.php.net/bug.php?id=43053, therefore when sorting numeric keys, if the key is of the form 0.00001 php will represent it as 1.0E-5.

These methods will assume this to be a string and therefore not organise your array as you may expect.

When using value of this form for array keys use sprintf('%f', 0.00001) to generate the key, for smaller values the precision needs to be included
e.g. sprintf('%0.10f', 0.00000001)

jakub dot lopuszanski at nasza-klasa dot pl ¶

11 years ago

Note that ksort will NOT help you much if numeric and string keys are mixed together.
$t = array(
  "a"=>"A",
  0=>"A",
  "b"=>"A",
  1=>"A"
);
var_dump($t);
ksort($t);
var_dump($t);
?>

produces (on PHP 5.3.6-4 with Suhosin-Patch) :

array(4) {
  ["a"]=>
  string(1) "A"
  [0]=>
  string(1) "A"
  ["b"]=>
  string(1) "A"
  [1]=>
  string(1) "A"
}

array(4) {
  ["b"]=>
  string(1) "A"
  [0]=>
  string(1) "A"
  ["a"]=>
  string(1) "A"
  [1]=>
  string(1) "A"
}

note that the second array should be sorted by keys, but is even more messed up than the first one!

maik dot riechert at animey dot net ¶

14 years ago

Be careful when using ksort for mixed type keys!!

$a = array(
    'first' => true,
    0       => 'sally',
);

$b = array(
    0       => 'sally',
    'first' => true,
);

ksort($a);
ksort($b);
var_dump($a);
var_dump($b);

Output is:
array(
    0 => 'sally',
    'first' => true,
)

array(
    'first' => true,
    0 => 'sally',
)

If you want same results for both arrays, use:

ksort($a, SORT_STRING);

The reason for that lays in the compare mechanism which would normally just typecast 'first' to an integer or 0 to a string when comparing it to each other. So you have to use SORT_STRING, otherwise you would lose information when 'first' is converted to int.

centraleffects at yahoo dot com ¶

9 years ago

I wrote this function to sort meta_value in wordpress. I tried a lot of array sorting but neither of them work. But this is not suitable for multidimensional array. This is intended only for wordpress meta_value

The problem is to sort below( the order should be ascending; alphabetically then numerically like A-Z then 0-9):
500-999 users
25-49 users
All Sizes
1-4 users
5-9 users
10-24 users
250-499 users
1000-4999
5000-9999

The solution:

function array_sort($arr){
    if(is_array($arr)){
        $numeric = array();
        $string = array();
        foreach($arr as $k => $v)
        {
            if(isset($v["meta_value"])){
                 $str = explode(" ",trim($v["meta_value"]));
                 $firstWord  = explode("-",trim($str[0]));
             }else{
                 $str = $v;
                 $firstWord  = explode("-",trim($str));
             }

            $firstWord = $firstWord[0];

            if(is_numeric($firstWord))
            {
                $numeric[(int)$firstWord] = $v;
            }else{
                $string[$firstWord] = $v;
            }
            unset($firstWord);
        }
        ksort($string,SORT_STRING);
        ksort($numeric,SORT_NUMERIC);

        return array_merge((array)$string, (array)$numeric);
    }

        return false;
}

The usage:
$meta =get_post_meta($post_id,$meta_key);
$sorted = array_sort($meta);

The result:
All Sizes
1-4 users
5-9 users
10-24 users
25-49 users
250-499 users
500-999 users
1000-4999
5000-9999