php将两个数组相同的key合并到一个数组

$arr = array(
    array(
    'id' => 1,
    'user_name'=>'test1'
    ),
    array(
    'id' => 2,
    'user_name'=>'test2'
    ),
    array(
    'id' => 3,
    'user_name'=>'test3'
    )
);
$arr2 = array(
     array(
    'id' => 1,
    'shop_name'=>'shop1'
    ),
    array(
    'id' => 5,
    'shop_name'=>'shop2'
    ),
    array(
    'id' => 3,
    'shop_name'=>'shop3'
    )
);
怎么根据2个数组id相同的一维数组，将$arr2的shop_name添加到$arr，如果没有相同的id，shop_name为空，形成如下数组：
$good_arr =array(
    array(
    'id' => 1,
    'user_name'=>'test1',
    'shop_name'=>'shop1'
    ),
    array(
    'id' => 2,
    'user_name'=>'test2',
    'shop_name'=>''
    ),
    array(
    'id' => 3,
    'user_name'=>'test3',
    'shop_name'=>'shop3'
    )
 
);

 

PHP5.5支持一个很棒的函数array_column()非常适合干这个事情，具体请参考手册:http://cn2.php.net/manual/zh/function.array-column.php。

$shop_name = array_column($arr2, 'shop_name', 'id');
foreach($arr as $key => $item) {
    $exist = array_key_exists($item['id'], $shop_name);
    $arr[$key]['shop_name'] = $exist ? $shop_name[$item['id']] : '';
}