Seems like an interesting effort. A developer is building an alternative Java-based backend to Lemmy’s Rust-based one, with the goal of building in a handful of different features. The dev is looking at using this compatibility to migrate their instance over to the new platform, while allowing the community to use their apps of choice.
PHP has been having a resurgence in popularity because it works.
PHP never went away. Wordpress, Mediawiki, Slack, Facebook, etc etc etc. IMO PHP is likely to have created the most wealth per line of code of all languages, including C (edit: since 2000). It’s completely under the radar.