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array_multisort
Sort multiple or multi-dimensional arrays
Description
bool array_multisort( array &$array1 , mixed $array1_sort_order = SORT_ASC, mixed $array1_sort_flags = SORT_REGULAR, mixed ...$rest )
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
Returns true on success or false on failure.
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.
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'];
}
// 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);
?>
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
)
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