相同下标数组元素相加

$a = [
  ['goods_id'=>2,'num'=>4],
  ['goods_id'=>2,'num'=>5],
  ['goods_id'=>4,'num'=>6],
  ['goods_id'=>4,'num'=>6],
  ['goods_id'=>4,'num'=>6]
];
$b = [];
echo "<pre>";
print_r($a);
foreach( $a as $key=>$val ){
   if( array_key_exists($val['goods_id'], $b) ){
       $b[$val['goods_id']]['num'] += $val['num'];
   }else{
      $b[$val['goods_id']] = $val;
   }
}
sort($b);
print_r($b);

 

转自：https://blog.youkuaiyun.com/wuxiaoxue22/article/details/80236494