Sort the entries by key

# ArrayObject::ksort

(PHP 5 >= 5.2.0, PHP 7, PHP 8)

ArrayObject::ksort — Sort the entries by key

### Description

public ArrayObject::ksort(int `$flags` = `SORT_REGULAR`): true

Sorts the entries by key, maintaining key to entry correlations. This is useful mainly for associative arrays.

> 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.

### Parameters

`flags`

  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`.

### Changelog

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

### Examples

Example #1 ArrayObject::ksort() example

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

The above example will output:

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

### See Also

- ArrayObject::asort() - Sort the entries by value
- ArrayObject::natsort() - Sort entries using a "natural order" algorithm
- ArrayObject::natcasesort() - Sort an array using a case insensitive "natural order" algorithm
- ArrayObject::uasort() - Sort the entries with a user-defined comparison function and maintain key association
- ArrayObject::uksort() - Sort the entries by keys using a user-defined comparison function
- ksort() - Sort an array by key in ascending order

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