CODEWITHSUNDEEP
phparrayssorting
strangeQuirks
strangeQuirks

Reputation: 5920

Sort array by keys ASC, then values ASC

I have a key => value array:

a => 2
c => 1
b => 3

I tried this:

ksort($result);
arsort($result);

But it doesn't work. I'm trying to sort by key alphabetically a-z and then sort it by value ascending 0-infinity.

so I should get

c => 1
a => 2
b => 3

But those sorts didn't give me what I wanted.

Upvotes: -1

Views: 773

Answers (2)

mario
mario

Reputation: 145482

I get unexpected results because sorting values that have the same value is unstable.

So what you forgot to mention in your question is that values can occur twice, and you want arrays sorted by values and keys secondarily.

c => 1
a => 2
z => 2
b => 3

There's no function for that in PHP. You could however try to sort by keys first ksort(), and then apply a user-defined function for sorting by value uasort(). In the callback it's important to also implement the $a == $b check and return 0. So the previous key-ordering might not be accidentally altered by +1 or -1 comparison states. (Don't know if that actually works.)

Otherwise you'll have to implement the whole sorting algorithm yourself, possibly separating keys and values in distinct maps.

Upvotes: 2

Justin Lucas
Justin Lucas

Reputation: 2321

Try using asort() instead of arsort(). arsort() will sort the array in reverse order. Something like this should "work":

$test = array(
    'a' => 0,
    'b' => 1,
    'c' => 2
);
ksort($test);
asort($test);

Mario is correct that this won't work if multiple items contain the same value. Alternatively, you could use uksort() which allows you to define exactly how the array is sorted. For example you could sort two items using their values by default. But if the values are the same sort by their keys.

$test = array(
    'a' => 2,
    'd' => 1,
    'c' => 1,
    'b' => 3
);
function cmp($a, $b){
    global $test;
    $val_a = $test[$a];
    $val_b = $test[$b];

    if($val_a == $val_b){
        return ($a < $b) ? -1 : 1;
    }
    return ($val_a < $val_b) ? -1 : 1;
}
uksort($test, 'cmp');

Upvotes: 9

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