Sort multiple or multi-dimensional arrays

# array_multisort

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

array_multisort — Sort multiple or multi-dimensional arrays

### Description

array_multisort(
array `&$array1`,
mixed `$array1_sort_order` = SORT_ASC,
mixed `$array1_sort_flags` = SORT_REGULAR,
mixed `...$rest`
): true

array_multisort() can be used to sort several arrays at once, or a multi-dimensional array by one or more dimensions.

Associative (string) keys will be maintained, but numeric keys will be re-indexed.

> 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

`array1`

  An array being sorted.

`array1_sort_order`

  The order used to sort the previous array argument. Either `SORT_ASC` to sort ascendingly or `SORT_DESC` to sort descendingly.

  This argument can be swapped with `array1_sort_flags` or omitted entirely, in which case `SORT_ASC` is assumed.

`array1_sort_flags`

  Sort options for the previous array argument:

  Sorting type flags:

  - `SORT_REGULAR` - compare items normally (don't change types)
  - `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

  This argument can be swapped with `array1_sort_order` or omitted entirely, in which case `SORT_REGULAR` is assumed.

`rest`

  More arrays, optionally followed by sort order and flags. Only elements corresponding to equivalent elements in previous arrays are compared. In other words, the sort is lexicographical.

### Return Values

Always returns `true`.

### Changelog

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

### Examples

Example #1 Sorting multiple arrays

`<?php
$ar1 = array(10, 100, 100, 0);
$ar2 = array(1, 3, 2, 4);
array_multisort($ar1, $ar2);
var_dump($ar1);
var_dump($ar2);
?>`

In this example, after sorting, the first array will contain 0, 10, 100, 100. The second array will contain 4, 1, 2, 3. The entries in the second array corresponding to the identical entries in the first array (100 and 100) were sorted as well.

    array(4) {
      [0]=> int(0)
      [1]=> int(10)
      [2]=> int(100)
      [3]=> int(100)
    }
    array(4) {
      [0]=> int(4)
      [1]=> int(1)
      [2]=> int(2)
      [3]=> int(3)
    }

Example #2 Sorting multi-dimensional array

`<?php
$ar = array(
array("10", 11, 100, 100, "a"),
array( 1, 2, "2", 3, 1)
);
array_multisort($ar[0], SORT_ASC, SORT_STRING,
$ar[1], SORT_NUMERIC, SORT_DESC);
var_dump($ar);
?>`

In this example, after sorting, the first array will transform to "10", 100, 100, 11, "a" (it was sorted as strings in ascending order). The second will contain 1, 3, "2", 2, 1 (sorted as numbers, in descending order).

    array(2) {
      [0]=> array(5) {
        [0]=> string(2) "10"
        [1]=> int(100)
        [2]=> int(100)
        [3]=> int(11)
        [4]=> string(1) "a"
      }
      [1]=> array(5) {
        [0]=> int(1)
        [1]=> int(3)
        [2]=> string(1) "2"
        [3]=> int(2)
        [4]=> int(1)
      }
    }

Example #3 Sorting database results

For this example, each element in the data array represents one row in a table. This type of dataset is typical of database records.

Example data:

    volume | edition
    -------+--------
        67 |       2
        86 |       1
        85 |       6
        98 |       2
        86 |       6
        67 |       7

The data as an array, called data. This would usually, for example, be obtained by looping with mysqli_fetch_assoc().

In this example, we will order by volume descending, edition ascending.

We have an array of rows, but array_multisort() requires an array of columns, so we use the below code to obtain the columns, then perform the sorting.

`<?php
// The data as created by looping over mysqli_fetch_assoc:
$data[] = array('volume' => 67, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 1);
$data[] = array('volume' => 85, 'edition' => 6);
$data[] = array('volume' => 98, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 6);
$data[] = array('volume' => 67, 'edition' => 7);
// Obtain a list of columns
foreach ($data as $key => $row) {
$volume[$key] = $row['volume'];
$edition[$key] = $row['edition'];
}
// You can use array_column() instead of the above code
$volume = array_column($data, 'volume');
$edition = array_column($data, 'edition');
// Sort the data with volume descending, edition ascending
// Add $data as the last parameter, to sort by the common key
array_multisort($volume, SORT_DESC, $edition, SORT_ASC, $data);
// Loop over the data and output the sorted values for each column
echo 'volume | edition', PHP_EOL;
echo '-------+--------', PHP_EOL;
for ($i = 0; $i < count($data); $i++) {
printf("%6d | %7d\n", $volume[$i], $edition[$i]);
}
?>`

The dataset is now sorted, and will look like this:

    volume | edition
    -------+--------
        98 |       2
        86 |       1
        86 |       6
        85 |       6
        67 |       2
        67 |       7

Example #4 Case insensitive sorting

Both `SORT_STRING` and `SORT_REGULAR` are case sensitive, strings starting with a capital letter will come before strings starting with a lowercase letter.

To perform a case insensitive sort, force the sorting order to be determined by a lowercase copy of the original array.

`<?php
$array = array('Alpha', 'atomic', 'Beta', 'bank');
$array_lowercase = array_map('strtolower', $array);
array_multisort($array_lowercase, SORT_ASC, SORT_STRING, $array);
print_r($array);
?>`

The above example will output:

    Array
    (
        [0] => Alpha
        [1] => atomic
        [2] => bank
        [3] => Beta
    )

### See Also

- usort() - Sort an array by values using a user-defined comparison function
- The comparison of array sorting functions

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