Encrypted session BLOB?

I don't think you get it ... There's no reliable way to read that data properly from "userland"; ONLY the PHP engine can do that. Even if it somehow works for you currently, that's a lucky dice roll, and it may break at any time.

If you think you "need" it, it's only because the data is already sitting there and you're looking for a shortcut to it. I know it's easy to fall into that trap, but it is a trap.