Migration to PHP 8 for a Legacy WordPress Multisite

A test-prep company's massive WordPress multisite gets an upgrade from end-of-life PHP to PHP 8 with zero downtime.

Client

Magoosh

Date

December 2022 – March 2023

Technologies

PHP 8, WordPress multisite, Docker, Playwright, Git, WP Engine, Query Monitor

My client’s massive WordPress multi-site was running on an end-of-life PHP version. Upgrading had been long-delayed because it’s risky: PHP 8 turns once-silent bugs in older plugins and themes into fatal errors that instantly take down even the most robust sites. To mitigate the risk of the migration, I audited the theme and dozens of plugins; all software found to be incompatible with modern PHP was painstakingly replaced on a copy of the site created in a Docker container and later on a live staging site. A suite of end-to-end tests were run before and after every change with Playwright JS. Finally, when all tests for all blogs passed, the migration shipped through git-based deployment with zero downtime.