[fChk]

I have planned to have members and their records maintained, so a registration system has been a requirement since the inception.

In this case then, indeed, a full-blown registration module is needed... and if you'll be sticking with PHP then I would still recommend redis or memcached as a NoSQL-database-solution to store sessions data. PHP has its own extensions to communicate with them... Again never use an RDBMS (MySQL, mariaDB etc..) for session storage unless you're out of options...

I actually installed nodejs on my backup server meaning to tinker with it about a month ago, but haven't made any time yet, and I'm still on the fence if nodejs is the best solution in my circumstance for interacting with redis. More reading is required.

I do like the idea of running a dual setup, with the persistent database to hold records, stats, trophies, items, the like, and a redis server handle more fluid data about character state: vector and position. But I think I'm a long ways off from that one: sql is still new to me and I think I'd benefit in the long run by acquiring more familiarity with sql before learning redis.

I've adopted Node.js since 2012 and I've coded (in JavaScript) a versatile Web server around it that I keep using anytime a REAL-TIME web application is needed.. I don't do Games, but a JavaScript-based Game is definetly a real-time app (in multi-player mode at least), never forget that... and that's my main message here and what I've read in your OP doesn't square well with this very fact (ie it will induce a huge latency penalty..)

Anyway, you can build a full PHP solution of your game, then you'll see for yourself its limitations. Then, after familiarizing yourself with Node.js and Redis in the back-end, try to port it with these Technologies and then you'll see the difference.

A Node.js-based Web server is an Async server and Redis stores data in memory in JSON form with a filesystem caching for persistence; that's where their high-performance comes from and that's why they are suited for real-time Apps development.

Good luck!