仅使用特定键值对“内部”数组进行排序 - 使用uasort（）？

Question

Array opareas
(
[0] => Array
(
[name] = => array('opname1')

[subcats] => Array
    (
        [0] => Array
            (
                [amount] => 9883
                [perc] => 112.61394712853236
            )

        [1] => Array
            (
                [amount] => 1
                [perc] => 0.011394712853236098
            )

        [2] => Array
            (
                [amount] => 3679
                [perc] => 41.921148587055605
            )

    )

)

[1] => Array
(
[name] = => array('opname2')

[subcats] => Array
    (
        [0] => Array
            (
                [amount] => 12166
                [perc] => 56.8584380987989
            )

        [1] => Array
            (
                [amount] => 1473
                [perc] => 6.884142636818245
            )

        [2] => Array
            (
                [amount] => 955
                [perc] => 4.463242510632331
            )

        [3] => Array
            (
                [amount] => 6802
                [perc] => 31.789503201383372
            )

    )

)

PHP is excellent for sorting arrays, but I can't figure out what to use when having this issue.. Take a look of the array above.

I want to sort innner subcats[] array by the perc-key from lower to higher.

I want the result to be:

Array opareas
(
[0] => Array
(
[name] = => array('opname1')

[subcats] => Array
    (
        [0] => Array
            (
                [amount] => 1
                [perc] => 0.011394712853236098 //Lowest percentage value
            )

        [1] => Array
            (
                [amount] => 3679
                [perc] => 41.921148587055605
            )

        [2] => Array
            (
                [amount] => 9883
                [perc] => 112.61394712853236 //Highest percentage value
            )

    )

)

[1] => Array
(
[name] = => array('opname2');

[subcats] => Array
    (
        [0] => Array
            (
                [amount] => 955
                [perc] => 4.463242510632331 //Lowest percentage value
            )

        [1] => Array
            (
                [amount] => 1473
                [perc] => 6.884142636818245
            )

        [2] => Array
            (
                [amount] => 12166
                [perc] => 56.8584380987989
            )

        [3] => Array
            (
                [amount] => 6802
                [perc] => 31.789503201383372 //Highest percentage value
            )

    )

)

I've tried with this:

class whateverArray {

    private function sort_subcats_perc($a, $b) {               
        if ($a['subcats']['perc'] == $b['subcats']['perc'] ) {return 0;}
        return ( $a['subcats']['perc'] < $b['subcats']['perc'] ) ? -1 : 1;
    }

    public function showStuff() {
       $opareas = array(); //Given above

       //Sort subcat array from low to high based on perc-key
       uasort( $opareas, array( $this, 'sort_subcats_perc') );
    }

 );

}

I don't want the actual opareas[0] and operas[1] to switch position (is what happens when using the function I've tried) in the array, I only WANT the inner array subcats[] to change it's order based on perc-field/key. Is this possible with uasort? Or any other builtin of PHP excellent sorting functions?

Answer 1

If you want to sort the sub-array, your comparison function needs to be a bit different. Then you can loop over the outer array by reference, so that the subcats will be sorted in place.

foreach ($opareas as &$value) {
    usort($value['subcats'], function($a, $b) {
        if ($a['perc'] > $b['perc']) return 1;
        if ($a['perc'] < $b['perc']) return -1;
        return 0;
    });
}
unset($value); // unset the reference after looping

You can use usort. You only need to use uasort if you care about the order of the keys in subcats.