How to sort an array of associative arrays by value of a given key in PHP?
Given this array:
$inventory = array(
array("type"=>"fruit", "price"=>3.50),
array("type"=>"milk", "price"=>2.90),
array("type"=>"pork", "price"=>5.43),
);
I would like to sort $inventory's elements by price to get:
$inventory = array(
array("type"=>"pork", "price"=>5.43),
array("type"=>"fruit", "price"=>3.50),
array("type"=>"milk", "price"=>2.90),
);
How can I do this?
19 Answers
You are right, the function you're looking for is array_multisort().
Here's an example taken straight from the manual and adapted to your case:
$price = array();
foreach ($inventory as $key => $row)
{
$price[$key] = $row['price'];
}
array_multisort($price, SORT_DESC, $inventory);
As of PHP 5.5.0 you can use array_column() instead of that foreach:
$price = array_column($inventory, 'price');
array_multisort($price, SORT_DESC, $inventory);
Answer
Since your array elements are arrays themselves with string keys, your best bet is to define a custom comparison function. It's pretty quick and easy to do. Try this:
function invenDescSort($item1,$item2)
{
if ($item1['price'] == $item2['price']) return 0;
return ($item1['price'] < $item2['price']) ? 1 : -1;
}
usort($inventory,'invenDescSort');
print_r($inventory);
Produces the following:
Array
(
[0] => Array
(
[type] => pork
[price] => 5.43
)
[1] => Array
(
[type] => fruit
[price] => 3.5
)
[2] => Array
(
[type] => milk
[price] => 2.9
)
)
I ended on this:
function sort_array_of_array(&$array, $subfield)
{
$sortarray = array();
foreach ($array as $key => $row)
{
$sortarray[$key] = $row[$subfield];
}
array_multisort($sortarray, SORT_ASC, $array);
}
Just call the function, passing the array and the name of the field of the second level array. Like:
sort_array_of_array($inventory, 'price');
You can use usort with anonymous function, e.g.
usort($inventory, function ($a, $b) { return strnatcmp($a['price'], $b['price']); });
I use uasort like this
<?php
$users = [
[
'username' => 'joe',
'age' => 11
],
[
'username' => 'rakoto',
'age' => 21
],
[
'username' => 'rabe',
'age' => 17
],
[
'username' => 'fy',
'age' => 19
],
];
uasort($users, function ($item, $compare) {
return $item['username'] >= $compare['username'];
});
var_dump($users);
This function is re-usable:
function usortarr(&$array, $key, $callback = 'strnatcasecmp') { uasort($array, function($a, $b) use($key, $callback) { return call_user_func($callback, $a[$key], $b[$key]); }); } For PHP 7 and later versions.
/**
* A method for sorting associative arrays by a key and a direction.
* Direction can be ASC or DESC.
*
* @param $array
* @param $key
* @param $direction
* @return mixed $array
*/
function sortAssociativeArrayByKey($array, $key, $direction){
switch ($direction){
case "ASC":
usort($array, function ($first, $second) use ($key) {
return $first[$key] <=> $second[$key];
});
break;
case "DESC":
usort($array, function ($first, $second) use ($key) {
return $second[$key] <=> $first[$key];
});
break;
default:
break;
}
return $array;
}
Usage:
$inventory = sortAssociativeArrayByKey($inventory, "price", "ASC");
uasort( $inventory, function ($a, $b) { if ( $a==$b ) return 0; else return ($a > $b) ? -1 : 1; });