> This lax behaviour for property definitions makes writing code around them harder. Especially when you take into account that any object can have properties dynamically added to them:

Doing so now raises a deprecation warning, unless you add #[AllowDynamicProperties], and PHP 9 will convert it to an error. I'm told this will simplify internals and unlock optimizations.

Arrays are still fairly awful, but generics may become a reality sooner rather than later, and on that could be built Vec and Dict types, à la Hack. PHP is going to be stuck with arrays as they are now for forever, but they'll at least become optional for new code.