Php 将值合并到数组时出错

我有一个数组

stdClass Object ( 
   [0] => Array ( [id] => 5353 [month] => 05 ) 
   [1] => Array ( [id] => 5542 [month] => 06 ) 
   [2] => Array ( [id] => 4676 [month] => 06 ) 
   [3] => Array ( [id] => 5542 [month] => 07 ) 
   [4] => Array ( [id] => 5542 [month] => 09 ) 
) 

stdClass Object ( 
   [0] => Array ( [id] => 5353 [month] => 05 ) 
   [1] => Array ( [id] => 5542 [month] => 06 ) 
   [2] => Array ( [id] => 4676 [month] => 06 ) 
   [3] => Array ( [id] => 5542 [month] => 07 ) 
   [4] => Array ( [id] => 5542 [month] => 09 ) 
) 

我想当数组中的一个键重复时，它将被添加到数组中 这是我的代码：

$result = array();
foreach ($object as $val) {
   if(!isset($result[$val['id']])) 
      $result[$val['id']] = $val;
   else
      $result[$val['id']]['month'] = array($result[$val['id']]['month'], $val['month']);
}
$result = array_values($result); // reindex array

结果:

Array ( 
   [0] => Array ( [id] => 5353 [month] => 05) 
   [1] => Array ( [id] => 5542 [month] => Array ( [0] => Array ( [0] => 06 [1] => 07 ) [1] => 09 ) ) 
   [2] => Array ( [id] => 4676 [month] => 06 ) 
)

如何将其固定到结果是：

Array ( 
   [0] => Array ( [id] => 5353 [month] => 05) 
   [1] => Array ( [id] => 5542 [month] => Array ( [0] => 06 [1] => 07 [2] => 09 ) )
   [2] => Array ( [id] => 4676 [month] => 06 ) 
)

但是，如何获得如下所示的stdClass对象

stdClass Object ( 
   [0] => Array ( [id] => 5353 [month] => 05 ) 
   [1] => Array ( [id] => 5542 [month] => 06 ) 
   [2] => Array ( [id] => 4676 [month] => 06 ) 
   [3] => Array ( [id] => 5542 [month] => 07 ) 
   [4] => Array ( [id] => 5542 [month] => 09 ) 
)