Analysis of the concepts and usage of abstract classes and abstract methods in PHP, php abstraction_PHP tutorial

Analysis of the concepts and usage of abstract classes and abstract methods in PHP, php abstraction

The examples in this article describe abstract classes and abstract methods in PHP. Share it with everyone for your reference, the details are as follows:

1. Abstract keyword: abstract

Abstract means that it cannot be explained exactly, but it has a certain concept or name. To declare an abstract class or method in PHP, we need to use the abstract keyword.

2. Definition of abstract methods and abstract classes

At least one method in a class is abstract, we call it an abstract class. So if you define an abstract class, first define the abstract method.

abstract class class1{
  abstract function fun1();
……
}

1. There is at least one abstract method in the class
2. Abstract methods are not allowed to have { }
3. Abstract methods must be preceded by abstract

3. Rules for using abstract classes and methods

Several characteristics of abstract classes:

1. cannot be instantiated and can only be inherited
2. In the inherited derived class, all abstract methods must be overloaded before they can be instantiated

Example:

<&#63;php
abstract class cl1{
  abstract function fun1();
  abstract function fun2();
}
class cl2 extends cl1{
  function fun1(){
    echo "第一个";
  }
  function fun2(){
    echo "第二个";
  }
}
$c=new cl2();
echo $c->fun2();
&#63;>

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I hope this article will be helpful to everyone in PHP programming.