Detailed explanation of method coverage in php

In object-oriented programming, method overriding is a very common operation. PHP is no exception, it allows us to override parent class methods in subclasses. In this article, I will introduce you to method overriding in PHP and how to use it to improve the flexibility and readability of your code.

What is method override?

In object-oriented programming, method overriding refers to redefining a method that has been defined in the parent class in the subclass. Specifically, when a method is defined in a subclass, its name, parameter list, and return type must be the same as the method defined in the parent class. Methods defined in a subclass will override methods in the parent class, that is, when we call the method, the method code in the subclass will be executed, not the code in the parent class.

Through method coverage, we can rewrite the methods of the parent class so that it can better adapt to the needs of the subclass. This not only improves code reusability and flexibility, but also makes the code clearer and easier to read.

Notes on method coverage

When using method coverage, you need to pay attention to the following points:

1. Redefined methods in subclasses The name must be the same as the method name defined in the parent class.
2. The access modifier of the method redefined in the subclass cannot be more strict than the method defined in the parent class.
3. The parameter list of the redefined method in the subclass must be the same as the method defined in the parent class.
4. The return type of the redefined method in the subclass must be the same or more specific than the method defined in the parent class.

For example, suppose we have an Animal class, which defines an eat method:

class Animal {
    public function eat() {
        echo "Animal is eating.";
    }
}

Then we define a Cat class, which inherits the Animal class, but needs to be rewritten eat method:

class Cat extends Animal {
    public function eat() {
        echo "Cat is eating.";
    }
}

In this example, the eat method in the Cat class overrides the eat method in the Animal class. When we create a Cat instance and call the eat method, "Cat is eating." instead of "Animal is eating." will be output.

Use the parent keyword to call the parent class method

When overriding the parent class method in the subclass, sometimes we need to call the parent class method that has been defined in the subclass method. To achieve this, PHP provides the parent keyword, which can be used to access methods in the parent class.

In a subclass, we can call methods already defined in the parent class in the following ways:

parent::method();

Where method is the name of the parent class method that needs to be called. In this way, it can be extended and improved without breaking the implementation of the parent class method.

For example, we can override the eat method in the Cat class and use the parent keyword to call the eat method in the Animal class:

class Cat extends Animal {
    public function eat() {
        parent::eat();
        echo "Cat is eating.";
    }
}

In this code, we first use parent ::eat() calls the eat method in the parent class Animal, and then outputs "Cat is eating.".

Summary

Method overriding is a very common operation when using object-oriented programming. Through method coverage, we can rewrite methods in the parent class to better adapt to the needs of the subclass and improve code reusability and flexibility. When using method overrides, you need to pay attention to restrictions on method names, access modifiers, parameter lists, and return types. At the same time, using the parent keyword in a subclass can call the parent class method to extend and improve the parent class method.

The above is the detailed content of Detailed explanation of method coverage in php. For more information, please follow other related articles on the PHP Chinese website!