PHP二维数组如何求和？

<?php
$arr = array(
0=>array(&#39;id&#39;=>1,&#39;tol&#39;=>10),
1=>array(&#39;id&#39;=>3,&#39;tol&#39;=>12),
2=>array(&#39;id&#39;=>8,&#39;tol&#39;=>5)
);
//输出tol值的和
echo array_sum(array_map(create_function(&#39;$val&#39;, &#39;return $val["tol"];&#39;), $arr));
?>

<?php
$arr = array(
0=>array(&#39;id&#39;=>1,&#39;tol&#39;=>10),
1=>array(&#39;id&#39;=>3,&#39;tol&#39;=>12),
2=>array(&#39;id&#39;=>8,&#39;tol&#39;=>5)
);

//输出
echo array_sum(array_map(function($val){return $val[&#39;tol&#39;];}, $arr));
?>

<?php
$arr = array(
0=>array(&#39;id&#39;=>1,&#39;tol&#39;=>10),
1=>array(&#39;id&#39;=>3,&#39;tol&#39;=>12),
2=>array(&#39;id&#39;=>8,&#39;tol&#39;=>5)
);

$sum = 0;

//foreach循环
foreach($arr as $item){
$sum += (int) $item[&#39;tol&#39;];
}

//输出
echo $sum;
?>

//根据字段last_name对数组$data进行降序排列
$last_names=array_column($data,'last_name');
array_multisort($last_names,SORT_DESC,$data);