Ask a PHP multi-dimensional array sorting problem

PHP Novice to ask a question;
The original array structure is as follows, the original array is sorted by Ads_id,time;
The requirement now is to reorder the NUM sums of the two-dimensional array

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] =&G T                 [TIME] = 2015-10 [ads_id] = 6) [1] = = Array (num] = Notoginseng [TIME] = 2015-11 [ads_id] =& Gt 6)) [7] = = Array ([0] = = Array ([nu M] = 280 [TIME] = 2015-10 [ads_id] = 7) [1] =       > Array         (num] = 343 [TIME] = 2015-11 [ads_id] + 7 )        ))

The

Final implementation is sorted as follows:

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] = [TIME] = 2015-10 [ads_id] = 6 ) [1] => Array ([num] = Notoginseng [TIME] = 2015-11 [ ADS_ID] = 6)))

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PHP Novice to ask a question;
The original array structure is as follows, the original array is sorted by Ads_id,time;
The requirement now is to reorder the NUM sums of the two-dimensional array

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] =&G T                 [TIME] = 2015-10 [ads_id] = 6) [1] = = Array (num] = Notoginseng [TIME] = 2015-11 [ads_id] =& Gt 6)) [7] = = Array ([0] = = Array ([nu M] = 280 [TIME] = 2015-10 [ads_id] = 7) [1] =       > Array         (num] = 343 [TIME] = 2015-11 [ads_id] + 7 )        ))

The

Final implementation is sorted as follows:

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] = [TIME] = 2015-10 [ads_id] = 6 ) [1] => Array ([num] = Notoginseng [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');

Using usort Custom Collations

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