Phalcon：无法在会话中更新数组中的值

I'm trying to update a value in session-Array, but it doesn't work. Initial set:

$bag = new SessionBag('p-' . $productId);
$bag->person = ['name' => 'john', 'age' => 25];

Then update:

$bag->person['age'] = 30;

After that the age is still 25 (checked in a xdebug-session).

If you enable warnings/notices on your web server, you will see something like "Notice: Indirect modification of overloaded property".

How to accomplish what you want?

$bag = new \Phalcon\Session\Bag('testest'); 
$bag->person = ['name' => 'john', 'age' => 25];
// $bag->person['age'] = 30; // Triggers Notice and will not work

$temp = $bag->person;
$temp['age'] = 44;
$bag->person = $temp;

print_r($bag);

[person] => Array ( [name] => john [age] => 44 )

If you are interested why this happens, you can read few explanations here PHP - Indirect modification of overloaded property