I’m using whatever the latest is, I think it’s currently 7.4. I like to get in the habit of using the latest version on my server simply because I’ll otherwise forget and stay on a low version which is pretty much what happened to everyone which is why 5.6 was around for so long.
WordPress has been forcing the new PHP version since last few months. And it seems like 7.2 would be fixed standard for next few years with the WordPress. I think PHP 5 is pretty much out for most of the PHP frameworks online.