Modify object serialize value - php

Question

I want to change the below object serialize values for 'secret_key' and 'public_key' and then i have to unserialize again.
What is the best way to modify (without string replace option)?
__PHP_Incomplete_Class Object
(
[__PHP_Incomplete_Class_Name] => RulesReactionRule
[*parent] =>
[id] => 51
[*elementId] => 1
[weight] => 0
[settings] => Array
(
)
[name] => commerce_payment_commerce_stripe
[label] => Stripe
[plugin] => reaction rule
[active] => 1
[status] => 3
[dirty] =>
[module] => commerce_payment
[owner] => rules
[access_exposed] => 0
[data] => __PHP_Incomplete_Class Object
*RECURSION*
[tags] => Array
(
[0] => Commerce Payment
)
[*children] => Array
(
[0] => __PHP_Incomplete_Class Object
(
[__PHP_Incomplete_Class_Name] => RulesAction
[*parent] => __PHP_Incomplete_Class Object
*RECURSION*
[id] =>
[*elementId] => 3
[weight] => 0
[settings] => Array
(
[commerce_order:select] => commerce-order
[payment_method] => Array
(
[method_id] => commerce_stripe
[settings] => Array
(
[stripe_currency] => USD
[secret_key] => sk_test_CCVVVVCC
[public_key] => pk_test_SDFFEFEF
[display_title] => Stripe
[cardonfile] => 1
[txn_type] => authorize
)
)
)
[*elementName] => commerce_payment_enable_commerce_stripe
)
)
[*info] => Array
(
)
[*conditions] => __PHP_Incomplete_Class Object
(
[__PHP_Incomplete_Class_Name] => RulesAnd
[*parent] => __PHP_Incomplete_Class Object
*RECURSION*
[id] =>
[*elementId] => 2
[weight] => 0
[settings] => Array
(
)
[*children] => Array
(
)
[*info] => Array
(
)
[*negate] =>
)
[*events] => Array
(
[0] => commerce_payment_methods
)
[*eventSettings] => Array
(
)
)