What is a “Final Class” in php?

“PHP 5 introduces the final keyword, which prevents child classes from overriding a method by prefixing the definition with final. If the class itself is being defined final then it cannot be extended”

https://www.php.net/manual/en/language.oop5.final.php#:~:text=PHP%205%20introduces%20the%20final,then%20it%20cannot%20be%20extended.&text=Note%3A%20Properties%20and%20constants%20cannot,may%20be%20declared%20as%20final.