php如何替换数组的key

// 需要替换 key 的数组
$arr_old = array(
    '0' => array('id' => 1, 'name' => 'Carroll'),
    '1' => array('id' => 2, 'name' => 'Chrdai'),
    '3' => array('id' => 3, 'name' => 'xiaodai'),
);

// 将新的key定义一个新数组
$key_name = array('key1','key2','key3');

// 现在开始替换
$arr_new = array_combine($key_name,$arr_old);

var_dump($arr_new);
/*
array (size=3)
  'key1' =>
    array (size=2)
      'id' => int 1
      'name' => string 'Carroll' (length=7)
  'key2' =>
    array (size=2)
      'id' => int 2
      'name' => string 'Chrdai' (length=6)
  'key3' =>
    array (size=2)
      'id' => int 3
      'name' => string 'xiaodai' (length=7)
*/