(PHP 4, PHP 5, PHP 7)
array_multisort — Sort multiple or multi-dimensional arrays
&$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.
array1An 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_flagsSort 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. Only elements corresponding to equivalent elements in previous arrays are compared. In other words, the sort is lexicographical.
Returns TRUE on success or FALSE on failure.
| 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.
|
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().
<?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 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
)