When to use Final in PHP

Question

Although I am aware of what a final class is, I am curious about how and when it is actually necessary.

<?php
final class Foo extends Bar
{
   public function()
   {
     echo 'John Doe';
   }
}

If I've got it right, "final" allows it to extend "Foo.".

Can somebody tell me when and why to use the word "final"? I.e., is there any justification for not extending a class?

It would be useful to construct a class that extends "Bar" if, for instance, classes "Foo" and "Bar" are missing some features.

Answer 1

I would advise against having a class final for general use. There may be some situations when it makes sense, such as when designing a complicated API or framework and wanting to ensure that users may only modify the functionality you want them to be able to control, restricting this option and making some base classes final.

For instance, it could be sensible to make an Integer class final to prevent users of your framework from modifying, let's say, the add(...) function in your class.