php中计算二维数组中某一元素之和

[0] => array(5) {
      ["id"] => string(2) "11"
      ["name"] => string(5) "1.jpg"
      ["suffix"] => string(3) "jpg"
      ["url"] => string(29) "./Uploads/1/5292f55d208e8.jpg"
      ["size"] => string(6) "715895"
    }
    [1] => array(5) {
      ["id"] => string(2) "12"
      ["name"] => string(22) "minisite数据库.docx"
      ["suffix"] => string(4) "docx"
      ["url"] => string(30) "./Uploads/1/5292f5606a52c.docx"
      ["size"] => string(5) "16667"
    }

我要计算size的和

（1）

echo array_sum(array_map(create_function('$val', 'return $val["size"];'), $arr));

或者

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

（2）

$sum = 0;

foreach($arr as $item){

  $sum += (int) $item['size'];

}