PHP Version for c5-8.5.2
What PHP version should I be using with Concrete5 8.5.2 ?
I'd highly recommend going with PHP 7.3, since performance is improved over older versions.
Another consideration, we are getting an increasing number of addons & themes coming through the PRB that specify higher php versions such as >=php7.2.
So as @PineCreativeLabs says, if your host has php7.3, then go for it.