If you are hosted by IPS, meaning you’ve purchased one of their cloud hosting packages, you don’t need to worry about the underlying version of PHP. When you upgrade in the ACP, IPS will take care of that for you. You only need to worry about the version of PHP if you’re self hosting.
Before you upgrade, I highly recommend switching to a default theme and disabling all third party applications first. Once the upgrade is complete, re-enable applications one at a time.