The Tumblr Engineering blog has a new post with details about how they made the switch to PHP 7 in their previously PHP 5 codebase (and some of the things they learned along the way).

At Tumblr, we’re always looking for new ways to improve the performance of the site. This means things like adding caching to heavily used codepaths, testing out new CDN configurations, or upgrading underlying software.

Recently, in a cross-team effort, we upgraded our full web server fleet from PHP 5 to PHP 7. The whole upgrade was a fun project with some very cool results, so we wanted to share it with you.

They start off with the timeline of events, starting with the original hackday project out through the final PHP 7 deployment in production less than a year later. They cover some of the testing methods they employed during the transition and the impact of the update on their application on request latency, CPU load and memory usage. They wrap up the post talking about some of the PHP 7-specific things they made use of in their update including anonymous functions and scalar type hinting.