将数据插入MongoDB的内部数组中

我有一点问题,希望你能帮助我.我在MongoDB中有下一个数组结构:

{
"_id":ObjectId("4e43cf96e7c7914b87d2e0ff"),
"list" :[
    {
    "id" : ObjectId("4e43cf96e62883ee06000002"),
    "user_name" : "login",
    "comments" : [ ]  //insert here new data
    },
    {
    "id" : ObjectId("4e43cf96e62883ee06000003"),
    "user_name" : "login",
    "comments" : [ ]
    }
]
}

我想通过"list.id"向评论中插入新数据.但我尝试这样:

$post_id = "4e43cf96e62883ee06000002";
$this->connection->user->feed->update(
    array ('list.id' => new MongoId($post_id) ), 
    array ('$push' => array ('list'=>array('comments'=>$data ) ))
)

但是该代码在结构中创建了新字段,但没有向字段'comments'添加数据:

{
"_id":ObjectId("4e43cf96e7c7914b87d2e0ff"),
"list" :[
     {
     "id" : ObjectId("4e43cf96e62883ee06000002"),
     "user_name" : "login",
     "comments" : [ ]  //insert here new data
     },    
     {
     "id" : ObjectId("4e43cf96e62883ee06000003"),
     "user_name" : "login",
     "comments" : [ ]
     },            
     {
     "comments" : { //added new field
        //there is my data
     }
]
}

我也尝试过:

$this->connection->user->feed->update(
     array ('list.id' => new MongoId($post_id) ), 
     array ('$push' => array ('list.comments'=>$data ) ) 
  );

但没什么.

这在mongo控制台上运行良好:)

db.yar.update({"list.id":ObjectId("4e43cf96e62883ee06000002")}, {"$addToSet":{"list.$.comments":"my cool comment"}});