請教一個php多維陣列排序問題

php新手請教一個問題；
原數組結構如下，原數組是按ads_id，time進行排序；
現在的需求是根據二維數組的num總和重新進行排序

Array(    [5] => Array        (            [0] => Array                (                    [num] => 840                    [time] => 2015-10                    [ads_id] => 5                )            [1] => Array                (                    [num] => 684                    [time] => 2015-11                    [ads_id] => 5                )        )    [6] => Array        (            [0] => Array                (                    [num] => 23                    [time] => 2015-10                    [ads_id] => 6                )            [1] => Array                (                    [num] => 37                    [time] => 2015-11                    [ads_id] => 6                )        )    [7] => Array        (            [0] => Array                (                    [num] => 280                    [time] => 2015-10                    [ads_id] => 7                )            [1] => Array                (                    [num] => 343                    [time] => 2015-11                    [ads_id] => 7                )        ))

最終實現排序如下：

Array(    [5] => Array        (            [0] => Array                (                    [num] => 840                    [time] => 2015-10                    [ads_id] => 5                )            [1] => Array                (                    [num] => 684                    [time] => 2015-11                    [ads_id] => 5                )        )            [7] => Array        (            [0] => Array                (                    [num] => 280                    [time] => 2015-10                    [ads_id] => 7                )            [1] => Array                (                    [num] => 343                    [time] => 2015-11                    [ads_id] => 7                )        )            [6] => Array        (            [0] => Array                (                    [num] => 23                    [time] => 2015-10                    [ads_id] => 6                )            [1] => Array                (                    [num] => 37                    [time] => 2015-11                    [ads_id] => 6                )        ))

回複內容：

php新手請教一個問題；
原數組結構如下，原數組是按ads_id，time進行排序；
現在的需求是根據二維數組的num總和重新進行排序

Array(    [5] => Array        (            [0] => Array                (                    [num] => 840                    [time] => 2015-10                    [ads_id] => 5                )            [1] => Array                (                    [num] => 684                    [time] => 2015-11                    [ads_id] => 5                )        )    [6] => Array        (            [0] => Array                (                    [num] => 23                    [time] => 2015-10                    [ads_id] => 6                )            [1] => Array                (                    [num] => 37                    [time] => 2015-11                    [ads_id] => 6                )        )    [7] => Array        (            [0] => Array                (                    [num] => 280                    [time] => 2015-10                    [ads_id] => 7                )            [1] => Array                (                    [num] => 343                    [time] => 2015-11                    [ads_id] => 7                )        ))

最終實現排序如下：

Array(    [5] => Array        (            [0] => Array                (                    [num] => 840                    [time] => 2015-10                    [ads_id] => 5                )            [1] => Array                (                    [num] => 684                    [time] => 2015-11                    [ads_id] => 5                )        )            [7] => Array        (            [0] => Array                (                    [num] => 280                    [time] => 2015-10                    [ads_id] => 7                )            [1] => Array                (                    [num] => 343                    [time] => 2015-11                    [ads_id] => 7                )        )            [6] => Array        (            [0] => Array                (                    [num] => 23                    [time] => 2015-10                    [ads_id] => 6                )            [1] => Array                (                    [num] => 37                    [time] => 2015-11                    [ads_id] => 6                )        ))

function mySort($a, $b) {    $sumA = 0;    $sumB = 0;    foreach($a as $ele) {        $sumA += $ele['num'];    }    foreach($b as $ele) {        $sumB += $ele['num'];    }    return $sumB < $sumA;}usort($arr, 'mySort');

使用 usort 自訂定序

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