php中计算二维数组中某一元素之和

$arr=array(
[0] => array(5) {
      ["id"] => string(2) "11"
      ["name"] => string(5) "张三"
      ["size"] => string(6) "715895"
    }
[1] => array(5) {
      ["id"] => string(2) "12"
      ["name"] => string(22) "李四"
      ["size"] => string(5) "16667"
    }
)

echo array_sum(array_map(function($val){return $val['size'];}, $arr));