What is the meaning of a final class and a final method?

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february 22, 2023, at 23:30

In PHP, the final keyword can be used to mark a class or method as "final", which means that it cannot be extended or overridden by any subclass.

A final class is a class that cannot be subclassed. In other words, it is a class that cannot have any child classes. Once a class is marked as final, no other class can extend it or inherit from it. This is often used to prevent further modification or extension of a class that is intended to be a "leaf" class in a class hierarchy.

Here is an example of a final class in PHP

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final class MyFinalClass {
    // Class implementation goes here
}
A final method, on the other hand, is a method that cannot be overridden by any subclass. In other words, once a method is marked as final in a parent class, no subclass can provide a different implementation of that method. This is often used to ensure that a specific behavior or functionality is preserved across all subclasses.

Here is an example of a final method in PHP

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class MyBaseClass {
    final public function myFinalMethod() {
        // Method implementation goes here
    }
}
class MySubclass extends MyBaseClass {
    // This code will generate a fatal error, because myFinalMethod is marked as final in MyBaseClass
    public function myFinalMethod() {
        // Method implementation goes here
    }
}
In general, marking a class or method as final can be useful in situations where you want to prevent further modification or extension of a class, or ensure that a specific behavior or functionality is preserved across all subclasses. However, it's important to use final sparingly and with care, as it can limit flexibility and make your code harder to modify and maintain in the future.