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array_multisort (PHP 4, PHP 5) array_multisort -- Sort multiple or multi-dimensional arrays Descriptionbool array_multisort ( array ar1 [, mixed arg [, mixed ... [, array ...]]] )
Returns TRUE on success or FALSE on failure.
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.
The input arrays are treated as columns of a table to be sorted
by rows - this resembles the functionality of SQL ORDER BY
clause. The first array is the primary one to sort by. The rows
(values) in that array that compare the same are sorted by the
next input array, and so on.
The argument structure of this function is a bit unusual, but
flexible. The first argument has to be an array. Subsequently,
each argument can be either an array or a sorting flag from the
following lists.
Sorting order flags:
Sorting type flags:
SORT_REGULAR - Compare items normally SORT_NUMERIC - Compare items numerically SORT_STRING - Compare items as strings
No two sorting flags of the same type can be specified after each
array. The sorting flags specified after an array argument apply
only to that array - they are reset to default SORT_ASC and
SORT_REGULAR before each new array argument.
Example 1. Sorting multiple arrays |
<?php
$ar1 = array("10", 100, 100, "a");
$ar2 = array(1, 3, "2", 1);
array_multisort($ar1, $ar2);
var_dump($ar1);
var_dump($ar2);
?>
|
In this example, after sorting, the first array will contain "10",
"a", 100, 100. The second array will contain 1, 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]=> string(2) "10"
[1]=> string(1) "a"
[2]=> int(100)
[3]=> int(100)
}
array(4) {
[0]=> int(1)
[1]=> int(1)
[2]=> string(1) "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);
$data[] = array('volume' => 67, 'edition' => 7);
?>
|
In this example, we will order by volume descending,
edition ascending.
We have an array of rows, but array_multisort()
requires an array of columns, so we use the below code to obtain the
columns, then perform the sorting.
|
<?php
foreach ($data as $key => $row) {
$volume[$key] = $row['volume'];
$edition[$key] = $row['edition'];
}
array_multisort($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
) |
|
User Contributed Notes
array_multisort
Michael Oelze at ÄM (myname) ÄT GMXdotDE
25-Apr-2005 11:15
I try array_multisort at first and it seems to work well. But then I program a page with cached datas (the arrays were saved in a session). Suddenly the sort function doesn't seem to work. There was no error in my script, so I try the reference on the variables. Then he manage to sort the arrays again.
So it seems that if you save your Arrays in a session your arrays are global variables and then 'array_multisort' doesn't sort the arrays despite it gives back 'true'.
You must reference your variables and all work well:
session_start(); // restore variables (Arrays etc.)
.....
.....
array_multisort(&$Array1,&$Array2,&$Array3,...);
....
$_SESSION["Array1"]=$Array1;//
$_SESSION["Array2"]=$Array2;//Save Arrays in Session Data
$_SESSION["Array3"]=$Array3;//
......
Now you can store your Data Arrays in your Session and are able to sort them as you like...
stevec at NO-/ dot /-SPAM dot qiguang dot net
13-Apr-2005 10:19
Be careful when using array_multisort() on copies of arrays, as you might end up changing the original array. Given the following code:
<?php
$test1 = array(4,3,2,1);
$test2 = $test1;
$test3 = array('a', 'b', 'c', 'd');
array_multisort($test2, SORT_ASC, $test3);
echo 'test1:';
print_r($test1);
echo 'test2:';
print_r($test2);
echo 'test3:';
print_r($test3);
?>
You would expect:
test1:Array
(
[0] => 4
[1] => 3
[2] => 2
[3] => 1
)
test2:Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
)
test3:Array
(
[0] => d
[1] => c
[2] => b
[3] => a
)
However, if you run the code, you actually get:
test1:Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
)
test2:Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
)
test3:Array
(
[0] => d
[1] => c
[2] => b
[3] => a
)
Note that the original ($test1) ends up being sorted even though it was never called by array_multisort(). To work around this, insert a statement to modify the copy ($test2) before calling array_multisort() on it. The following code will produce the expected "correct" results:
<?php
$test1 = array(4,3,2,1);
$test2 = $test1;
$test3 = array('a', 'b', 'c', 'd');
$test2[0] = $test2[0]; array_multisort($test2, SORT_ASC, $test3);
echo 'test1:';
print_r($test1);
echo 'test2:';
print_r($test2);
echo 'test3:';
print_r($test3);
?>
This seems to be a resurrection of the closed bug #8130. Also, someone reported this behavior in bug #32031, but it was incorrectly labeled "bogus" in reference to bug #25359, which is a different issue.
joao at intrasystems dot com dot br
07-Apr-2005 02:27
Exemple of sorting multi-dimensional arrays by one of it's fields:
$result[0]['nome']='Joao';
$result[0]['order']=5;
$result[1]['nome']='Pedro';
$result[1]['order']=1;
$result[2]['nome']='Marcelo';
$result[2]['order']=3;
foreach($result as $res)
$sortAux[] = $res['order'];
array_multisort($sortAux, SORT_ASC, $result);
print_r($result);
produces:
Array
(
[0] => Array
(
[nome] => Pedro
[order] => 1
)
[1] => Array
(
[nome] => Marcelo
[order] => 3
)
[2] => Array
(
[nome] => Joao
[order] => 5
)
)
Toni
10-Nov-2004 05:30
An example to sort an array by 3 criteria:
$recordset is an array of results from a query to a database, that I sort using $matrix as auxiliary array. First numeric, Second and Third alphabetically.
<?php
for($idx=0;$idx<$toShow;$idx++){
$matrix[0][$id]=$recordset[$id][0];
$matrix[1][$id]=$recordset[$id][1];
$matrix[2][$id]=$recordset[$id][10];
}
array_multisort($matrix[0], SORT_DESC, SORT_NUMERIC,$matrix[1], SORT_STRING, SORT_ASC,$matrix[2], SORT_STRING, SORT_ASC);
?>
meddle at dzygn.com
05-Oct-2004 09:40
If you want to sort a multidomensional array by key name you cannot use array_multisort. ie: for an array named $archivos that prints like this:
Array
(
[0] => Array
(
[index] => 0
[name] => test
)
[1] => Array
(
[index] => 0
[name] => watertaxi.jpg
)
[2] => Array
(
[index] => 0
[name] => 2_0003.JPG
)
[3] => Array
(
[index] => 0
[name] => 24A_0025.JPG
)
[4] => Array
(
[index] => 1
[name] => _CIMG3501.JPG
)
)
If I wanted to order by "name" I'd use:
function comparar($a, $b) {
return strnatcasecmp($a["name"], $b["name"]);
}
usort($archivos, "comparar");
This function performs a case insensitive string comparison using a "natural order" algorithm (strnatcasecmp), resulting in:
Array
(
[0] => Array
(
[index] => 0
[name] => 2_0003.JPG
)
[1] => Array
(
[index] => 0
[name] => 24A_0025.JPG
)
[2] => Array
(
[index] => 0
[name] => test
)
[3] => Array
(
[index] => 0
[name] => watertaxi.jpg
)
[4] => Array
(
[index] => 1
[name] => _CIMG3501.JPG
)
)
kat dot n0spam at audiogalaxy dot com
24-Aug-2001 12:25
If you're having problems with array_multisort changing variables in global space when it is called inside a function and you're not passing in the function parameters by reference you can alleviate the problem by calling array_multisort with its parameters by reference.
array_multisort(&$a, SORT_DESC, &$b);
More details here in my bug report:
http://www.php.net/bugs.php?id=12936
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array_merge