Yes PHP 7 is supported providing you run at least IonCube Loader 6.
What is PHP Version 7?
The first stable version of PHP 7 is version 7.0.0 which was released in December 2015. The current PHP 7 version is 7.1.7 which was released in July 2017 and will remain supported until December 2019.
SubscriptionBoss requires at least PHP version 5.3 to operate correctly and hence any version of PHP 7 will do however you are of course recommended to use the most recent stable versions which is 7.0.21. or 7.1.7.
Is My Site Running PHP Version 7?
If you have you have been with your host less than a year and are running on a shared server then you are almost certainly running PHP 7 already.
Your host provider should be able to tell you what version of PHP you are running on your server or you can check yourself. See How To Find What version of PHP my site is running?
How To Upgrade My Web Site to PHP 7
The easiest way to get this done is to ask your web site host to upgrade your site to PHP 7. Many hosts will have a self-install feature in cPanel that allows you to choose which version of PHP to run.
If you prefer to do this yourself the latest version of PHP can de downloaded at from the PHP Downloads page
After upgrading to PHP 7 make sure you also get your host to upgrade IonCube Loader too