php foreach循环判断在改变值。坐等大神解决

    foreach ($gjtc as $key=>$val)
    {
        foreach ($gjtc2 as $key2=>$vals2)
        {
            if($key['order_id']==$key2['order_id'])
            {

            }
        }
    }

写到这里不会写了,我要把2数组sp_tc相加根据1组的ID

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直接用sql语句操作就好了，为什么还要php写循环去操作呢？