Sort array by highest key=>value

Question

I want to sort an array highest to lowest by the value of amount. My array $res is as follows:

Array
(
    [0] => 1
    [id] => 1
    [1] => Testowy 1
    [user] => Testowy 1
    [2] => 150
    [amount] => 150
    [3] => 1,2,3
    [what] => 1,2,3
    [4] => Polska
    [country] => Polska
    [5] => 1
    [platform] => 1
)
Array
(
    [0] => 2
    [id] => 2
    [1] => Testowy 2
    [user] => Testowy 2
    [2] => 100
    [amount] => 100
    [3] => 1
    [what] => 1
    [4] => United States
    [country] => United States
    [5] => 2
    [platform] => 2
)

I tried using max and arsort, but none of those seem to accept which key they should use for sorting. Any help?

I'm just guessing here, but if this result is the result of a db query, you could also sort in the query by using e.g. ORDER BY — djheru, Aug 14 '13 at 19:26
possible duplicate of [Reference: all basic ways to sort arrays and data in PHP](http://stackoverflow.com/questions/17364127/reference-all-basic-ways-to-sort-arrays-and-data-in-php) — deceze, Aug 14 '13 at 19:27

Ben Miller · Answer 1 · 2013-08-14T19:50:07.790

1

Try usort

function cmp($a, $b)
{
    return ($a["amount"]<=$b["amount"])?-1:1;
}

usort($array, "cmp");

edited Aug 14 '13 at 19:50

answered Aug 14 '13 at 19:24

Ben Miller

29
7

Maybe dont use strcmp, but a simple '>' cause amount is no string at all. Maybe wrong for sorting '1 and 10'. – dognose Aug 14 '13 at 19:38
Now you are missing the equal case :) `return ($a["amount"]>=$b["amount"])` (`>=` or `<=` depending on the sorting order) will be enough. – dognose Aug 14 '13 at 19:43

Expedito · Answer 2 · 2013-08-14T19:46:40.283

1

usort($res, function ($a, $b){
    return $b['amount'] - $a['amount'];
});
print_r($res);

For versions of PHP < 5.3, use the following:

function cmp($a, $b){
    return $b['amount'] - $a['amount'];
}
usort($res, "cmp");

edited Aug 14 '13 at 19:46

answered Aug 14 '13 at 19:36

Expedito

7,771
5
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I tried `usort`, but I'm getting `usort() expects parameter 1 to be array, boolean given`. `$res` is from `while($res = mysql_fetch_array($query))`. – Tomek Buszewski Aug 14 '13 at 20:55
Isn't `mysql_fetch_array` returning array? – Tomek Buszewski Aug 14 '13 at 21:00
@TomekBuszewski - It should be, but you wouldn't be getting an error like that unless you were trying to feed `usort` a boolean value. Why don't you try dumping `$res` to see what you get. – Expedito Aug 14 '13 at 21:02
I used `print_r($res)` and I pasted it in my question. – Tomek Buszewski Aug 14 '13 at 21:03

Marcin Orlowski · Answer 3 · 2013-08-14T22:08:54.373

0

Use sorting functions with user defined comparators, like: usort:

http://php.net/usort

Then your comparator gets two objects and tells (by any logic you want) which one is greater):

function compare($a, $b) {
    $result = -1;
    if( $a["amount"] == $b["amount"]) {
      $result = 0;
    } else {
       if( $a["amount"] > $b["amount"] ) {
          $result = 1;
       }
    }

    return $result;
}

usort($res, "compare");

edited Aug 14 '13 at 22:08

answered Aug 14 '13 at 19:24

Marcin Orlowski

72,056
11
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141

is the `1` in `$a1`->`($a1, $b)` a typo? – Sean Aug 14 '13 at 19:35
Overkill. Simplest function Body: `return ($a["amount"]>=$b["amount"])` (`>=` or `<=` depending on the sorting order) (or the substraction Version of Pe de Leao) – dognose Aug 14 '13 at 19:41
@dognose: nope. it's answer for newbie for him to understand. No place for tricks – Marcin Orlowski Aug 14 '13 at 22:09

Sort array by highest key=>value

3 Answers3