multidimensional array session container in zend f

问题:

I am working on an application using zend framework 2 session array containers. I can create the session using array containers as mentioned in zend 2 document, but i am getting the problem while creating the session with multidimensional arrays. I want to update the session everytime since i am updating the values for shopping cart. I am trying with the below code, its not updated rather the session values are getting changed.

$container = new Container('test');
$values = array();
$values['one'] = '1';
$values['two'] = '2';
$container->item = $values; // Now the session contains the $values array 1,2


$container = new Container('test');
$values['one'] = '3';
$values['two'] = '4';
$container->item = $values; // Here the session values are 3,4 and 1,2 is not updating

I tried also with OffsetGet and OffsetSet methods as below, but the session values are not updated.

$container = new Container('test');
$session = $container->offsetGet('item');
$values['one'] = '3';
$values['two'] = '4';
$session = $container->offsetSet('item', $values); // results are 3,4

I am expecting the results as below,

Array
(
    [0] => Array
        (
            [values] => Array
                (
                    [one] => 1
                    [two] => 2
                )

        )

    [1] => Array
        (
            [values] => Array
                (
                    [one] => 3
                    [two] => 4
                )

        )

)

How i can obtain the multidimensional session arrays in zend 2 ? Thanks.