It introduced such drastic breaking changes, that probably a lot of systems which were previously perfectly serving their users will be abandoned. Projects that could have stayed on the internet and served their users just fine.
It broke the order of parameters in join statements.
It broke calling static functions without the need to declare them as static.
It broke adding properties dynamicly to objects.
It broke easy string handling for many functions where Null was rendered as an empty string.
And these changes make PHP code more bloated. There is now no way around adding more declarations to your codebase than before.
Some of these breakages had 30% votes against them, including the original author of PHP:
https://wiki.php.net/rfc/deprecate_dynamic_properties
The bar for breaking changes should be much higher.
Python's update from version 2 to version 3 caused a lot of pain. But at least it made the code leaner. Allowing users to go from "a=float(b)/c" to "a=b/c" is a good thing. Forcing users to go from "function f()" to "static function f()" is a bad thing.