How to access vBulletin session info from other PHP applications on the same domain?

[vbSuperfan]

I coding a small, simple light-weight PHP application (that is, I would like to avoid having to make it a full fledged "product"/plugin for vBulletin 5 Connect at this point) which must access the userid (and subsequently, username and usertitle) of the currently logged-in user in the vBulletin 5 Connect instance that is running on the same domain (that is, my PHP app will have access to the cookies of this vBulletin instance too).

My question is, what would be the simplest and most efficient way to get hold of this currently-logged-in-user-in-vBulletin information from this stand-alone PHP application of mine?

I'm guessing that the vBulletin user-sessions are not written to the database, but rather only using some kind of "memory only" PHP session kind of thing, which in turn would prevent me from using a database-only solution where all the above-mentioned information could be resolved directly from the vBulletin database by my application (based on initially looking up the session ID found in the vBulletin cookies etc), right?

Is there any good summarized info available for vBulletin 5 Connect for this kind of "Single Sign-On" functionality that anyone here knows of?

During my googling, I only managed to find similar info applying to vBulletin 3 (e.g. here), which I've heard has a very different user session handling than vBulletin 5 Connect though?

Any hints of any kind would be highly appreciated!