Sort multiple or multi-dimensional arrays

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# array_multisort

(PHP 4, PHP 5)

array_multisort — Sort multiple or multi-dimensional arrays

### Description

bool array_multisort ( array `&$array1` [, mixed `$array1_sort_order` = SORT_ASC [, mixed `$array1_sort_flags` = SORT_REGULAR [, mixed `$...` ]]] )

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.

### 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.

`...`

  More arrays, optionally followed by sort order and flags.

### Return Values

Returns `TRUE` on success or `FALSE` on failure.

### Changelog

Version | Description
--- | ---
5.4.0 | The `SORT_NATURAL` and `SORT_FLAG_CASE` were added to `array1_sort_flags` as possible sort flags.
5.3.0 | The `SORT_LOCALE_STRING` was added to `array1_sort_flags` as possible sort flags.

### 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 mysql_fetch_assoc().

`<?php
$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);
?>`

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
// Obtain a list of columns
foreach ($data as $key => $row) {
$volume[$key] = $row['volume'];
$edition[$key] = $row['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);
?>`

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 search, 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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