二维数组变一维数组，统计键值总和

首先我们先写好我们的sql语句，这里我的一个sql是三表联查的一个例子

 $sql = "select `order` .*,`info`.goodsnum as snum ,`realtion`.upagentid as upid from ".tablename("表1")." as `order`

left join ".tablename("表2")." as `realtion` on `order`.id = `realtion`.orderid 

left join ".tablename("表3")." as `info` on `order`.id =`info`.orderid 

where `realtion`.upagentid = $id and `order`.`status` in (2,3) and `order`.addtime >= $start and `order`.addtime < $end ";

    $total = pdo_fetchall($sql);
        //写一个方法把二维数组变成一维数组
        function add_num($total)
             {
                static $new=array();
                 foreach ($total as $k => $v) {
                     $new[$v["id"]]=$v["snum"];//循环获取二维数组里面的id然后重新放到一个新的数组里面，后面是你想要的那个值
                 }
                 return $new;
              }
         $add = add_num($total);

         $sum = 0; 
         //上面处理的一维数组在循环  把键值循环相加
         foreach($add as $key=>$value) 
         { 
            $sum+= $value; 
         } 
         $newtotal = $sum;
         $monthaddup = $price*$newtotal;
         print_r($monthaddup);