使用pid作為新數組的鍵值

$returnarr = array();
foreach($data as $val) {
    if(isset($returnarr[$val['pid']])) {
        $returnarr[$val['pid']]['amount'] += $val['amount']; 
    } else {
        $returnarr[$val['pid']]['pid'] = $val['pid'];
        $returnarr[$val['pid']]['amount'] = $val['amount']; 
    }
}

写个循环，根据pid 判断是否存在相同的然后合并，最后生成一个新的数组OK

$allok = array();
            foreach ($all as $key1 => &$value1){
                foreach ($value1 as $key2 => $value2){
                    $allok[$value2['pid']] = $value2;
                    $allok[$value2['pid']] = $allok[$value2['pid']]['amount'] + $value2['amount'];
                    /*$queryproductshop = Model('Product')->queryidshop($value2['pid']);
                    $queryshopclass = Model('ProductClassify')->SaleConfigShopClass($queryproductshop['cid']);
                    $queryproductshop['class'] = $queryshopclass['title'];
                    $allshop[] = $queryproductshop;*/
                }
            }
            dump($allok);

已经自己解决，自己想太复杂了

//代码如下，希望对你有帮助。
$orderInfo = array(

[0]=>
    'pid'=>7,
    'amount'=>1,
[1]=>
    'pid'=>7,
    'amount'=>2,
[2]=>
    'pid'=>8,
    'amount'=>1,

);
foreach ($orderInfo as $k=>$v)

          {
              $bKey=$v['pid'];
              if(!array_key_exists($bKey, $orderArr)) 
              {
                $orderArr[$bKey] = [];
                $sumData[$bKey] = 0;
                }
              $orderArr[$bKey]=$v;
              $sumData[$bKey]+=$orderArr[$bKey]['amount']; 
              $orderArr[$bKey]['amount']=$sumData[$bKey];
          }   
    var_dump($orderArr);