PHP 7.1.2. Fully supported with IPS 4.1.
I'm using the latest version of the PHP 5.6 branch. Not upgrading to PHP 7 yet because of possible incompatible add-ons for the scripts I use.
Been using 7.2.0alpha on both WordPress and XenForo installations. It seems to work pretty well and haven't had any breaking issues.
Anyone else using 7.2.4 now? I only do simple things thus far, but I haven't had any problems with it.
I'm still learning, but I am very soon going to be doing commercial work for clients, so I was wondering what the caveats are as I'm have been in a long test cycle really and if something doesn't work at the moment it's no money lost and actually a good learning experience. I have been thinking of using 7.1.x for production work I'm going to be doing soon though. From what I have seen it's about maybe a 10% decrease in performance, but I'm not the expert on that either. Thanks for the info though it is definitely appreciated.