php apcu_add class instance

Question

In the project that I am working on (PHP 7, Slim Framework), there is a service class that needs alot of time to get instanciated. In order to improve the overall performance of the system I though that an implementation as a singleton would help. I decided to use apcu in order to store the class instance and then fetch whenever needed.

My code for adding the instance to the cache is

$config = [ .... ];
if (!apcu_exists("mediaService")) {
     $mediaService = new \Services\MediaService($config);
     apcu_add("mediaService", $mediaService);
}

When I run it PHP Fatal error: Uncaught Exception: Serialization of 'Closure' is not allowed.

Any thoughts?