Usage scenarios and examples of final keyword in PHP

Usage scenarios and examples of the final keyword in PHP

In PHP, the final keyword is used to limit the inheritance and override (Override) of classes, methods and properties. By using the final keyword, you can ensure that certain code cannot be modified or overwritten in subclasses, improving the security and stability of the code.

1. Final is used for class definition
   By declaring a class as final, you can prevent other classes from inheriting the class. This is useful in certain situations, such as to protect a security-critical class from being modified or extended by other classes.

The sample code is as follows:

final class MyClass {
// ... class definition
}

class AnotherClass extends MyClass { // An error will be reported here and the final class cannot be inherited.
// ...
}

2. final is used for the definition of methods
   By declaring a method as final, you can prevent sub-classes from being inherited. An override of this method in the class. This can avoid accidental modification of method implementation in subclasses in some cases and improve the maintainability and stability of the code.

The sample code is as follows:

class ParentClass {
final public function myMethod() {

  // ... 方法实现

}
}

class ChildClass extends ParentClass {
public function myMethod() { // An error will be reported here and the final method cannot be overridden

  // ...

}
}

3. final is used for attributes The definition
   is similar to a method. By declaring a property as final, you can prevent the property from being overridden in subclasses. This can ensure that the value of a certain attribute will not be modified in some cases, improving code security.

The sample code is as follows:

class ParentClass {
final public $myAttribute = "Hello";

public function myMethod() {

  echo $this->myAttribute;

}
}

class ChildClass extends ParentClass {
public $myAttribute = "World"; // An error will be reported here and the final attribute cannot be overridden
}

$object = new ChildClass();
$object->myMethod(); // Output: Hello

Summary:
The final keyword is used in PHP to limit classes, methods and Inheritance and rewriting of attributes improve the security and stability of the code. By using the final keyword, you can avoid potential problems caused by accidental modification of code in subclasses. In actual development, using the final keyword is a good choice for key classes, methods and properties that do not want to be modified or extended.

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