对象数组

大师们帮我看一下这个数组，我要输出数组里的book_id,chapter_id该怎么输出啊

Array
(
  [0] => stdClass Object
  (
  [bookmark] => Array
  (
  [0] => stdClass Object
  (
  [create_time] => 1318905719
  [book_id] => 85251
  [page_index] => 1
  [param1] => 4994
  [param2] => 6699
  [time_version] => 1319693381
  [type] => 1
  [flag] => 1
  [chapter_id] => 150160
  )
 
  [1] => stdClass Object
  (
  [book_id] => 234234
  [page_index] => 1
  [param1] => 5594
  [param2] => 6699
  [time_version] => 1319694381
  [filename] => 234234_31_30.sqb
  [chapter_filename] => 181.sqc
  [type] => 3
  [flag] => 0
  [chapter_id] => 2452
  )
 
  )
 
  )
 
)

get_object_vars

请提出var_export($arr)的结果。

$arr[0]->bookmark[0]->book_id;
$arr[0]->bookmark[1]->chapter_id;