Wayfair is one of the world's largest online destinations for the home. Our storefront is a very large PHP application -- 3.5M LoC interacting with a wide array of extensions -- that serves 2M daily visitors. So we were delighted when our upgrade to PHP7 went without a hitch. It worked so well because of a test plan that covered a wide range of strategies and tools. This case study will combine a walkthrough of this project with a practical tour of PHP testing tools, from PHPUnit to GDB.