ksort()

(PHP 4, PHP 5, PHP 7)

对数组按照键名排序

说明

对数组按照键名排序，保留键名到数据的关联。本函数主要用于关联数组。

参数

输入的数组。

可以用可选参数$sort_flags改变排序的行为，详情见sort()。

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

Example #1ksort()例子

以上例程会输出：

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

参见

• asort() 对数组进行排序并保持索引关系
• 数组排序函数对比

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:

Output from first var_dump:
[0]=>
 array(3) {
  ["name"]=>
  string(3) "Bob"
  ["age"]=>
  int(8)
  ["colour"]=>
  string(3) "red"
 }
 [1]=>
 array(3) {
  ["name"]=>
  string(4) "Greg"
  ["age"]=>
  int(12)
  ["colour"]=>
  string(4) "blue"
 }
 [2]=>
 array(3) {
  ["name"]=>
  string(4) "Andy"
  ["age"]=>
  int(5)
  ["colour"]=>
  string(6) "purple"
 }
}
Output from 2nd var_dump:
array(3) {
 [0]=>
 array(3) {
  ["name"]=>
  string(4) "Greg"
  ["age"]=>
  int(12)
  ["colour"]=>
  string(4) "blue"
 }
 [1]=>
 array(3) {
  ["name"]=>
  string(3) "Bob"
  ["age"]=>
  int(8)
  ["colour"]=>
  string(3) "red"
 }
 [2]=>
 array(3) {
  ["name"]=>
  string(4) "Andy"
  ["age"]=>
  int(5)
  ["colour"]=>
  string(6) "purple"
 }
There's no checking on whether your array keys exist, or the array data you are searching on is actually there, but easy enough to add.

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;
}

I wrote this function to sort the keys of an array using an array of keynames, in order. 

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);
   }
  }
 }

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

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

Example

This will be the output of the example:
/*DESCENDING SORT*/
array(3) {
 ["peter"]=>
 array(2) {
  ["age"]=>
  int(21)
  ["gender"]=>
  string(4) "male"
 }
 ["mary"]=>
 array(2) {
  ["age"]=>
  int(20)
  ["gender"]=>
  string(6) "female"
 }
 ["john"]=>
 array(2) {
  ["age"]=>
  int(19)
  ["gender"]=>
  string(4) "male"
 }
}
/*ASCENDING SORT*/
array(3) {
 ["john"]=>
 array(2) {
  ["age"]=>
  int(19)
  ["gender"]=>
  string(4) "male"
 }
 ["mary"]=>
 array(2) {
  ["age"]=>
  int(20)
  ["gender"]=>
  string(6) "female"
 }
 ["peter"]=>
 array(2) {
  ["age"]=>
  int(21)
  ["gender"]=>
  string(4) "male"
 }
}

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.

A real quick way to do a case-insensitive sort of an array keyed by strings:
uksort($myArray, "strnatcasecmp");

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: 

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;
}

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
)

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

Note that ksort will NOT help you much if numeric and string keys are mixed together.

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!

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

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)

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.

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