PHP二维数组转一位数组

array.php

<?php
//一个很大的二维数组
$arr = array(
	0 => array(
		'id'=>11,
		'name'=>'name1'
	),
	1 => array(
		'id'=>22,
		'name'=>'name2'
	),
	2 => array(
		'id'=>33,
		'name'=>'name3'
	)

);

//如何以最高的效率实现将上面的二维数组转为一位数组
array(
	0 => 11,
	1 => 22,
	2 => 33
)

$final = array();

 foreach ($arr as $key => $val) {
     $final[] = $val['id'];
 }
 var_dump($final);