What is an abstract class in php? how to use?

Abstract class: At least one method in a class is abstract, we call it an abstract class.

Requirements:

1. There must be at least one abstract method in a class

2. Abstract methods are not allowed to have {}

3. Abstract

must be added in front of the abstract method. Example: Adding abstract

<?php 
    abstract class Human {
        public abstract function getInfo () {
            echo &#39;我是getInfo&#39;;
        }
    }
?>

in front of the class defines an abstract class of Human. There is an abstract method in the abstract class. When executed, an error is reported.

Fatal error: Abstract function Human::getInfo() cannot contain body

Abstract methods cannot have a text part (no method body), and the curly braces need to be removed

<?php 
    abstract class Human {
        public abstract function getUserInfo ();
        public abstract function getWalletInfo ();
    }
    
    class Student extends Human {
        public function getUserInfo () {
            echo &#39;getinfo&#39;;
        }
        
        public function getWalletInfo () {
            echo &#39;getwalletInfo&#39;;
        }
    }
    
    $Tom = new Student();
    $Tom -> getUserInfo();
    $Tom -> getWalletInfo ();
?>

Note:

1. Abstract classes cannot be Instantiated, can only be inherited.
2. In the inherited derived class, all abstract methods must be overloaded before instantiation

abstract class Human {
    public abstract function getUserInfo ();
    public abstract function getWalletInfo ();
}

class Student extends Human {
    public function getUserInfo () {
        echo 'getinfo';
    }
    
    // public function getWalletInfo () {
    //     echo 'getwalletInfo';
    // }
}

$Tom = new Student();

For example, if the derived class lacks a getWalletInfo() method, new will fail

The meaning of abstract class: When a derived class inherits an abstract class, it must use the naming rules of the abstract class to establish methods, otherwise the derived class is not allowed to be instantiated. In fact, it declares a specification to achieve The purpose of normative methods.

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