Analysis of concepts and usage examples of abstract classes and abstract methods in PHP

This article mainly introduces the concepts and usage of abstract classes and abstract methods in PHP. It analyzes the keywords, definitions, usage methods and related precautions of abstract classes and abstract methods in PHP in more detail. Friends in need can refer to it. Next

1. Abstract keyword: abstract

Abstract means that it cannot be explained exactly, but it has a certain concept or name. Declare one in PHP For abstract classes or methods we need to use the abstract keyword.

2. Definition of abstract methods and abstract classes

If 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 must be at least one abstract method in the class
2,Abstract methods are not allowed { }
3. Abstract methods must be preceded by abstract

3. Rules for using abstract classes and methods

Abstract Several characteristics of classes:

1. cannot be instantiated, but can only be inherited.
2. All abstract methods must be overloaded in the inherited derived class. Instantiation

Instance:

<?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();
?>

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