This handy function sorts associative arrays by a given child key but also allows you to keep numerical indices. By default, array_multisort() — which is useful for this kind of thing — removes the keys.
<?php
function sortAssocArrayByValue($arrayToSort, $sortKey, $isAsc = true, $keepKeys = false) {
if ($isAsc === true) {
$sort = SORT_ASC;
} else {
$sort = SORT_DESC;
}
$array = [];
$data = [];
// The keys are preserved by making them strings
foreach ($arrayToSort as $key => $value) {
if ($keepKeys === true) {
$k = '_' . $key;
} else {
$k = $key;
}
$data[$k] = $value;
$array[$k] = $value[$sortKey];
}
// This sorts the data based on $array
array_multisort($array, $sort, $data);
// If the keys are not being kept then the work is done
if ($keepKeys === false) {
return $data;
}
// To keep the keys the new array overwrites the old one and the numerical keys are restored
$arrayToSort = [];
foreach ($data as $key => $value) {
$arrayToSort[ltrim($key, '_')] = $value;
}
return $arrayToSort;
}
// A test numerical array
$array1 = [
['name' => 'TV', 'price' => 499.99],
['name' => 'Power cable', 'price' => 9.99],
['name' => 'Laptop', 'price' => 990.00]
];
// A test associative array
$array2 = [
'tv' => ['name' => 'TV', 'price' => 499.99],
'cable' => ['name' => 'Power cable', 'price' => 9.99],
'laptop' => ['name' => 'Laptop', 'price' => 990.00]
];
?>
<pre>
Numerical array, keys kept:
<?php print_r(sortAssocArrayByValue($array1, 'name', true, true)) ?>
<?php print_r(sortAssocArrayByValue($array1, 'name', false, true)) ?>
<?php print_r(sortAssocArrayByValue($array1, 'price', true, true)) ?>
<?php print_r(sortAssocArrayByValue($array1, 'price', false, true)) ?>
Numerical array, keys reset:
<?php print_r(sortAssocArrayByValue($array1, 'name', true, false)) ?>
<?php print_r(sortAssocArrayByValue($array1, 'name', false, false)) ?>
<?php print_r(sortAssocArrayByValue($array1, 'price', true, false)) ?>
<?php print_r(sortAssocArrayByValue($array1, 'price', false, false)) ?>
Associative array:
<?php print_r(sortAssocArrayByValue($array2, 'name', true)) ?>
<?php print_r(sortAssocArrayByValue($array2, 'name', false)) ?>
<?php print_r(sortAssocArrayByValue($array2, 'price', true)) ?>
<?php print_r(sortAssocArrayByValue($array2, 'price', false)) ?>
</pre>
<?php
/*
Output:
Numerical array, keys kept:
Array
(
[2] => Array
(
[name] => Laptop
[price] => 990.00
)
[1] => Array
(
[name] => Power cable
[price] => 9.99
)
[0] => Array
(
[name] => TV
[price] => 499.99
)
)
Array
(
[0] => Array
(
[name] => TV
[price] => 499.99
)
[1] => Array
(
[name] => Power cable
[price] => 9.99
)
[2] => Array
(
[name] => Laptop
[price] => 990.00
)
)
Array
(
[1] => Array
(
[name] => Power cable
[price] => 9.99
)
[0] => Array
(
[name] => TV
[price] => 499.99
)
[2] => Array
(
[name] => Laptop
[price] => 990.00
)
)
Array
(
[2] => Array
(
[name] => Laptop
[price] => 990.00
)
[0] => Array
(
[name] => TV
[price] => 499.99
)
[1] => Array
(
[name] => Power cable
[price] => 9.99
)
)
Numerical array, keys reset:
Array
(
[0] => Array
(
[name] => Laptop
[price] => 990.00
)
[1] => Array
(
[name] => Power cable
[price] => 9.99
)
[2] => Array
(
[name] => TV
[price] => 499.99
)
)
Array
(
[0] => Array
(
[name] => TV
[price] => 499.99
)
[1] => Array
(
[name] => Power cable
[price] => 9.99
)
[2] => Array
(
[name] => Laptop
[price] => 990.00
)
)
Array
(
[0] => Array
(
[name] => Power cable
[price] => 9.99
)
[1] => Array
(
[name] => TV
[price] => 499.99
)
[2] => Array
(
[name] => Laptop
[price] => 990.00
)
)
Array
(
[0] => Array
(
[name] => Laptop
[price] => 990.00
)
[1] => Array
(
[name] => TV
[price] => 499.99
)
[2] => Array
(
[name] => Power cable
[price] => 9.99
)
)
Associative array:
Array
(
[laptop] => Array
(
[name] => Laptop
[price] => 990.00
)
[cable] => Array
(
[name] => Power cable
[price] => 9.99
)
[tv] => Array
(
[name] => TV
[price] => 499.99
)
)
Array
(
[tv] => Array
(
[name] => TV
[price] => 499.99
)
[cable] => Array
(
[name] => Power cable
[price] => 9.99
)
[laptop] => Array
(
[name] => Laptop
[price] => 990.00
)
)
Array
(
[cable] => Array
(
[name] => Power cable
[price] => 9.99
)
[tv] => Array
(
[name] => TV
[price] => 499.99
)
[laptop] => Array
(
[name] => Laptop
[price] => 990.00
)
)
Array
(
[laptop] => Array
(
[name] => Laptop
[price] => 990.00
)
[tv] => Array
(
[name] => TV
[price] => 499.99
)
[cable] => Array
(
[name] => Power cable
[price] => 9.99
)
)
*/
?>
Tim Bennett is a freelance web designer from Leeds. He has a First Class Honours degree in Computing from
Leeds Metropolitan University and currently runs his own one-man web design company, Texelate.