How to use the protected keyword in PHP and what to pay attention to

How to use and pay attention to the protected keyword in PHP

In object-oriented programming in PHP, the protected keyword is used to define protected properties and methods. Unlike the public keyword, the properties and methods of the protected keyword can only be accessed within the own class and subclasses, and cannot be accessed outside the class.

First, let’s take a look at how to use the protected keyword to define protected properties and methods. In a class, we can use the protected keyword to mark a property or method, as shown below:

class MyClass {
   protected $name;
   
   protected function sayHello() {
      echo "Hello World!";
   }
}

In this example, the $name attribute and the sayHello() method are both marked as protected. This means that they can only be accessed and called within the MyClass class and its subclasses.

When we create a subclass that inherits from MyClass, the subclass will be able to access and call the protected properties and methods of the parent class. As shown below:

class MyChildClass extends MyClass {
   public function getName() {
      return $this->name;
   }
   
   public function greeting() {
      $this->sayHello();
   }
}

In this example, the MyChildClass class inherits the MyClass class, so the $name attribute and the sayHello() method can be used. We defined a getName() method to get the value of the $name attribute, and a greeting() method to call the sayHello() method.

Next, let us understand some things to note when using the protected keyword:

1. Protected properties and methods can only be accessed or called inside the class, not outside the class. for a visit. This provides a way to encapsulate and protect the implementation details of a class.
2. Subclasses can access and call the protected properties and methods of the parent class, but the parent class cannot access and call the protected properties and methods of the subclass.
3. If the protected method of the parent class is overridden in the subclass, you can use the parent keyword to call the method of the parent class.
4. Properties and methods protected by the protected keyword can be combined with other access modifiers (such as public and private) to achieve more complex access control.
5. Using the protected keyword to protect properties and methods can increase the maintainability and security of the code and prevent irrelevant code from modifying or accessing it.

In short, the protected keyword is used in PHP to define protected properties and methods, allowing us to access and call them inside the class and in subclasses. Using the protected keyword can improve the encapsulation and security of the code, making our code more maintainable and extensible. At the same time, we need to pay attention to some of the matters mentioned above when using the protected keyword to make full use of the characteristics of this keyword.

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