Final classes and methods in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the <code>final</code> keyword do when used with a class in PHP?

It prevents the class from being extended (inherited) by any other class. No child class can be created from a final class.

beginner

What happens if you try to extend a <code>final</code> class in PHP?

PHP will throw a fatal error because final classes cannot be extended.

beginner

What does the final keyword do when used with a method in PHP?

It prevents the method from being overridden in any child class.

intermediate

Can a final method be declared in a non-final class?

Yes, a method can be declared final even if the class itself is not final. This means the method cannot be overridden, but the class can still be extended.

intermediate

Why would you use final classes or methods in your PHP code?

To protect important classes or methods from being changed or extended, ensuring consistent behavior and preventing accidental overrides.

What will happen if you try to extend a final class in PHP?

A The class is extended successfully

B A fatal error occurs

C A warning is shown but code runs

D The final keyword is ignored

Final classes cannot be extended. Trying to do so causes a fatal error.

Which keyword prevents a method from being overridden in a child class?

A final

B private

C abstract

D static

The final keyword on a method stops child classes from overriding it.

Can a final method exist inside a non-final class?

A Only if the class is abstract

B No, methods cannot be final unless the class is final

C Only if the method is static

D Yes, methods can be final even if the class is not

Final methods can be declared inside non-final classes to prevent overriding.

What is the main reason to declare a class as final?

A To allow multiple inheritance

B To make the class abstract

C To prevent the class from being extended

D To allow method overriding

Declaring a class final stops other classes from extending it.

If a method is declared final, what can child classes NOT do?

A Override the method

B Use the method

C Call the method

D Declare the method as static

Final methods cannot be overridden by child classes.

Explain what a final class is and why you might use it in PHP.

Think about how final classes stop inheritance.

Describe the difference between a final class and a final method in PHP.

Focus on what each final keyword protects.