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What is the use of the final keyword in PHP? I believe many inexperienced people don't know what to do about it. Therefore, this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

The use of final keyword in PHP

The use of the final keyword is very simple, and the most important role in PHP is to define methods that cannot be rewritten. What is an unrewritable method? The method with the same name cannot be redefined even after the subclass inherits.

Class A {

Final function testA () {

Echo 'This is class Aids, PHP_EOL

}

}

Class childA extends A {

/ / Fatal error: Cannot override final method A::testA ()

Function testA () {

Echo 'This is class childA', PHP_EOL

}

}

If you add this keyword before the class definition, the class is also uninheritable.

Final class B {

Function testB () {

Echo 'This is class bundles, PHP_EOL

}

}

/ / Fatal error: Class childB may not inherit from final class (B)

Class childB extends B {

}

Thus, the meaning of the final keyword is the same as its own, and this class or method is immutable. Can this keyword be used in the interface? Of course, the answer is no, the meaning of the interface itself is to define a contract for the implementation class to implement, if the final keyword is defined, then the meaning of the interface does not exist, so from the language level, the interface and the methods in the interface cannot use the final keyword.

Interface C {

/ / Fatal error: Access type for interface method C::testC () must be omitted

Final function testC ()

}

In Java, final can also be used to define constants, but in PHP, class constants are defined through const. So final can't define variables.

After reading the above, have you mastered the method of using the final keyword in PHP? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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