What are the keywords for php to implement inheritance?

The keyword for php to implement inheritance is "extends". Only the single inheritance mode can be used in PHP, that is, a class can only inherit data directly from another class; and class inheritance needs to be achieved through the "extends" keyword, the syntax is "class subclass name extends parent class name {.. . ...}".

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

One of the great benefits of object-oriented programming (OOP) That is, you can use a class to inherit another existing class. The inherited class is called a parent class or base class, and the class that inherits this parent class is called a subclass. Subclasses can inherit the methods and properties of the parent class, so inheritance can improve code reusability and improve software development efficiency.

Subclasses can add new functions beyond those of the parent class, so the subclass can also be called an "extension" of the parent class. In addition, subclasses can also inherit the constructor of the parent class. When the subclass is instantiated, PHP will first search for the constructor in the subclass. If the subclass has its own constructor, PHP will call the constructor in the subclass first. When there is no constructor in the subclass, PHP will call the constructor in the parent class.

Class inheritance needs to be implemented through the extends keyword. The syntax format is as follows:

class 子类名 extends 父类名{
    ... ...
}

Note: Unlike languages ​​such as Java, in PHP, a class can only directly inherit data from one class, that is, single inheritance. But a class can have multiple subclasses.

Example:

<?php
class Person {
    var $name;
    var $age;
    function say() {
        echo "我的名字叫：".$this->name."<br />";
echo "我的年龄是：".$this->age;
    }
}
// 类的继承
class Student extends Person {
    var $school;    //学生所在学校的属性
    function study() {
        echo "我的名子叫：".$this->name."<br />";
        echo "我正在".$this->school."学习";
    }
}
$t1 = new Student();
$t1->name = "张三";
$t1->school = "人民大学";
$t1->study();
?>

Run this example, output:

我的名子叫：张三
我正在人民大学学习

In software development, the inheritance of classes makes the software created open It is an effective method for information organization and classification. It simplifies the workload of creating objects and classes and increases the reproducibility of code. Using inheritance provides a standardized hierarchical structure of classes. Through the inheritance relationship of classes, public features can be shared, improving the reusability of software.

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