Recipe 4.19 Sorting Multiple Arrays
4.19.1 Problem
You
want to sort multiple arrays or an array with multiple dimensions.
4.19.2 Solution
Use array_multisort(
):
To sort multiple arrays simultaneously,
pass multiple arrays to array_multisort( ):
$colors = array('Red', 'White', 'Blue');
$cities = array('Boston', 'New York', 'Chicago');
array_multisort($colors, $cities);
print_r($colors);
print_r($cities);
Array
(
[0] => Blue
[1] => Red
[2] => White
)
Array
(
[0] => Chicago
[1] => Boston
[2] => New York
)
To sort multiple dimensions within a
single array, pass the specific array elements:
$stuff = array('colors' => array('Red', 'White', 'Blue'),
'cities' => array('Boston', 'New York', 'Chicago'));
array_multisort($stuff['colors'], $stuff['cities']);
print_r($stuff);
Array
(
[colors] => Array
(
[0] => Blue
[1] => Red
[2] => White
)
[cities] => Array
(
[0] => Chicago
[1] => Boston
[2] => New York
)
)
To modify the sort type, as in
sort( ), pass in SORT_REGULAR,
SORT_NUMERIC, or SORT_STRING
after the array. To modify the sort order, unlike in sort(
), pass in SORT_ASC or
SORT_DESC after the array. You can also pass in
both a sort type and a sort order after the array.
4.19.3 Discussion
The array_multisort( ) function can sort several
arrays at once or a multidimensional array by one or more dimensions.
The arrays are treated as columns of a table to be sorted by rows.
The first array is the main one to sort by; all the items in the
other arrays are reordered based on the sorted order of the first
array. If items in the first array compare as equal, the sort order
is determined by the second array, and so on.
The default sorting values are SORT_REGULAR and
SORT_ASC, and they're reset after
each array, so there's no reason to pass either of
these two values, except for clarity.
$numbers = array(0, 1, 2, 3);
$letters = array('a', 'b', 'c', 'd');
array_multisort($numbers, SORT_NUMERIC, SORT_DESC,
$letters, SORT_STRING , SORT_DESC);
This example reverses the arrays.
4.19.4 See Also
Recipe 4.17 for simple sorting and Recipe 4.18 for sorting with a custom function;
documentation on array_multisort( ) at
http://www.php.net/array-multisort.
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