Yay!
https://caniphp.com/ is updated to include new features and deprecations for PHP v8.4.
This tool is like caniuse.com but for PHP – it tells you which features are in which versions and rounds up resources related to those features.
You can explore the PHP 8.4 changes at:
https://caniphp.com/?version=8.4
(Ironically, no PHP is used in the creation of this site!)