Abstract class and abstract method concepts and usage analysis _php techniques in PHP

The examples in this article describe abstract classes and abstract methods in PHP. Share to everyone for your reference, specific as follows:

One, abstract key words: abstract

Abstraction is not an exact description, but there is a certain concept or name, in PHP to declare an abstract class or method we need to use the Adstract keyword.

Definitions of abstract methods and abstract classes

At least one of the methods in a class is abstract, which we call an abstract class. So if defining an abstract class first defines an abstract method.

Abstract class class1{
  abstract function fun1 ();
...
}

1. There is at least one abstract method in the class
2, the abstract method does not allow {}
3, the abstract method must be added abstract before

Iii. abstract class and method usage rules

Several features of abstract classes:

1, cannot be instantiated, can only be inherited
2, in the inherited derived class, all abstract method overloads are to be instantiated

Instance:

<?php
abstract class cl1{
  abstract function fun1 ();
  Abstract function fun2 ();
}
Class Cl2 extends cl1{
  function fun1 () {
    echo "first";
  }
  function fun2 () {
    echo ' second ';
  }
}
$c =new Cl2 ();
echo $c->fun2 ();
? >

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I hope this article will help you with the PHP program design.