Changelog #27
Upgrading your site's PHP version will improve the security, performance, and supportability of your site.
Older software is more likely to contain code that is incompatible with recent PHP versions. Before you upgrade your PHP version, please make a multidev and run the upgrade in that space prior to testing it against the Development environment. We have already tested against a variety of Web Theme sites to make sure the release is eligible for our entire campus roster of sites, but we likely have not tested your particular site(s).
Learn more about PHP upgrades on the Pantheon website.