I'm trying to reach an element in an object array. But I couldn't succeed. 
Let's think this as an object called $result
How can I reach maskedNumber? 

```
Braintree_Result_Successful Object
(
    [success] => 1
    [_returnObjectName:private] => customer
    [customer] => Braintree_Customer Object
        (
            [_attributes:protected] => Array
                (
                    [creditCards] => Array
                        (
                            [0] => Braintree_CreditCard Object
                                (
                                    [_attributes] => Array
                                        (
                                            [maskedNumber] => ***********5897

```