With apcu you're going to pay the cost of serializing/deserializing the data.

If you dump your read heavy data into a PHP file on disk, that just has a return of your generated data, you can be benefit from having that bytecode compiled data stored in opcache for free (for the entire lifetime of the php-fpm service, or until you reach the maximum opcache allocateable memory).

I think that PHP gives you a few nice utilities to handle sharing, but they are problem specific. For example you might also spawn threads within a background PHP task, and there is shared memory functionality you can use in that case as well which is going to be faster than apcu or opcache.