OTOH, I'd say language changes/improvements, PSR, the tooling of course (Composer/Packagist, tons of CLI tools), the frameworks (Laravel or Symfony, with CakePH

OTOH, I'd say language changes/improvements, PSR, the tooling of course (Composer/Packagist, tons of CLI tools), the frameworks (Laravel or Symfony, with CakePHP & CodeIgniter still rocking, also micro-frameworks like Slim/Lumen), the libraries (Symfony components, FriendsOfPHP, thephpleague.com), debugging (PHPStan, Phan, Psalm, PHP Insights), refactoring (PHP CS Fixer, PHP_CodeSniffer, Rector), async/event driven (Open Swoole, ReactPHP). On Linux, production multi-PHP deployment is dead-simple thanks to the excellent DEB.SURY.ORG (for DEB based distros) and REMI (for RPM based distros) repos. It's also more common to deploy PHP via PHP-FPM and Nginx nowadays. Homebrew does a decent job on macOS too, multi-PHP deployment is also easy when coupled with Nginx/PHP-FPM. For Windows I have no idea but as long as you got XAMPP and MAMP, well :) Lots of Docker based solutions too like LocalWP (not just for WP), Lando, Laragon, DDEV to name a few. There's also excellent support in editors/IDEs, either by default (in JetBrain's PHPStorm, Nova, KDevelop or Kate Editor) or via plugins for VSCode, Sublime Text, Atom and others.