php array_walk vs foreach

gistfile1.txt

<?php
$arr0 = array(
    'aa' => array(
        'aa_1' => array('value' => 1, 'name' => 'aa1'),
        'aa_2' => array('value' => 2, 'name' => 'aa2'),
        'aa_3' => array('value' => 3, 'name' => 'aa3'),
    ),  
    'ab' => array(
        'ab_1' => array('value' => 4, 'name' => 'ab1'),
    ),  
    'ac' => array(
        'ac_1' => array('value' => 5, 'name' => 'ac1'),
    ),  
); 
$arr1 = array(
    'aa_1' => array('value' => 1, 'name' => 'aa1'),
    'aa_2' => array('value' => 2, 'name' => 'aa2'),
    'aa_3' => array('value' => 3, 'name' => 'aa3'),
    'ab_1' => array('value' => 4, 'name' => 'ab1'),
    'ac_1' => array('value' => 5, 'name' => 'ac1'),
); 
//将$arr0变为$arr1
//法1 foreach
foreach (array_values($arr0) as $k => $v)
{
    $k == 0 && $tmp = $v;
    $tmp = array_merge($tmp, $v);
}
foreach ($tmp as $v)
{
    $arr1[$v['value']] = $v['name'];
}

//法2 array_walk
$arr1 = array();
array_walk($arr0, function($items, $key){ global $arr1; $arr1 = $arr1+$items; });