Push new value to inner array with Lithium and MongoDB

I have a structure like this:

[_id] => MongoId Object (
    [$id] => 4e91bcb40b7aab256c000000
)
[campaigns] => Array (
    [0] => Array (
        [campaign_id] => 4e91bcd10b7aab2b6c000000
        [refer_code] => AjZCJR
        [owner] => 1
        [campaign_name] => Test Campaign
        [users] => Array (
        )
    )
    [1开发者_开发问答] => Array (
        [campaign_id] => 4e9210600b7aab276c000000
        [refer_code] => FQIMJd
        [owner] => 1
        [campaign_name] => New Test Campaign
        [users] => Array (
        )
    )
)

I would like to be able to update the campaigns array with new fields and update the existing fields, on the match of the ID.

Currently I am trying to do the following:

$data = array('campaign_name'=>'changed', 'new_field'=>'its new');
User::update(array('$push'=>array('campaigns.$'=>$data)),array('campaigns.campaign_id'=>$campaign_id));

However that is not working - I'm using the positional operator in order to try and match the array to the condition statement, as without it, it just creates a new array within the campaigns array.

I understand I am probably using it wrong, as I presume it should be used by doing

'campaigns.$.campaign_name'=>'changed'

However I don't want to be limited to specifying it each time, and was wondering the best way to do this type of update without using a for loop and adding each piece of data (which I'm currently doing as follows:)

$data = array();
foreach($this->request->data as $key=>$value) {
    $data['campaigns.$.'.$key] = $value;
}
User::update($data,array('campaigns.campaign_id'=>$campaign_id));

If someone could let me know the 'proper' way to do this, that would be great!

Thanks :)

Dan

---

Just update:

$co = array(
        '$pull' => array('campaigns.1" => array('campaign_name' => 'changed'' ) )
);

$p->update(array("_id" => new MongoId( $MongoID  )), $co);