What Is an Abstract Method

This section describes what is an abstract method - a method which only has only the calling signature declared with no implementation code. An abstract method must be fully implemented in subclasses. This means that any class with an abstract method must be declared as an abstract class.

What Is an Abstract Method? An abstract method is a method which only has only the calling signature declared with no implementation code. An abstract method must be fully implemented in subclasses. This means that any class with an abstract method must be declared as an abstract class.

In PHP, an abstract method is declared with the keyword "abstract". For example, the following tutorial example provides an abstract class MyShape2 with an abstract method showArea() which is required to be implemented by subclasses.

<?php 
/* MyCircle2.php
#- Copyright (c) 2015-2019, HerongYang.com, All Rights Reserved.
*/

abstract class MyShape2 {
   public $x;
   public $y;
   public $type;

   public function __construct($x,$y,$t) {
      $this->x = $x;
      $this->y = $y;
      $this->type = $t;
   }
   public function showType() {
     echo "   Type: " . $this->type ."\n";
   }
   public function showCenter() {
     echo "   Center: " . $this->x .", " . $this->y ."\n";
   }
   abstract public function showArea();
}

class MyCircle2 extends MyShape2 {
   public $radius;

   public function __construct($x,$y,$r) {
      parent::__construct($x,$y,"Circle");
      $this->radius = $r;
   }
   public function showArea() {
      echo "   Area: " . 3.1459*$this->radius**2 ."\n";
   }
}

  $object = new MyCircle2(1.0,2.0,0.5);
  
  echo "MyCircle object: \n";
  $object->showType();
  $object->showCenter();
  $object->showArea();
?>

If you run the above tutorial example, you will get something like this:

C:\herong> \php\php MyCircle2.php

MyCircle object:
   Type: Circle
   Center: 1, 2
   Area: 0.786475

Last update: 2019.

Table of Contents

 About This Book

 Introduction and Installation of PHP 7.3

 PHP Script File Syntax

 PHP Data Types and Data Literals

 Variables, References, and Constants

 Expressions, Operations and Type Conversions

 Conditional Statements - "if" and "switch"

 Loop Statements - "while", "for", and "do ... while"

 Function Declaration, Arguments, and Return Values

 Arrays - Ordered Maps

Introduction of Class and Object

 What Is a Class

 What Is an Object

 What Is a Constructor

 What Is a Static Method

 What Is a Static Variable

 What Is a Superclass and a Subclass

 What Is an Abstract Class

What Is an Abstract Method

 What Is an Interface

 What Is a Trait

 What Is an Overloaded Property

 What Is an Overloaded Method

 What Is Object Property Iteration

 What Is Object Cloning

 What Is Object Serialization

 What Is in an Object Variable

 Updating Variables Who Share an Object

 Passing Objects as Function Arguments

 Integrating PHP with Apache Web Server

 Retrieving Information from HTTP Requests

 Creating and Managing Sessions in PHP Scripts

 Sending and Receiving Cookies in PHP Scripts

 Controlling HTTP Response Header Lines in PHP Scripts

 MySQL Server Connection and Access Functions

 Functions to Manage Directories, Files and Images

 SOAP Extension Function and Calling Web Services

 SOAP Server Functions and Examples

 Localization Overview of Web Applications

 Using Non-ASCII Characters in HTML Documents

 Using Non-ASCII Characters as PHP Script String Literals

 Receiving Non-ASCII Characters from Input Forms

 "mbstring" Extension and Non-ASCII Encoding Management

 Managing Non-ASCII Character Strings with MySQL Servers

 Configuring and Sending out Emails

 Outdated Tutorials

 References

 Full Version in PDF/EPUB