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, 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:

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

Last update: 2015.

Table of Contents

 About This Book

 Introduction and Installation of PHP 7.0

 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

 Configuring and Sending out Emails

 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

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

 Outdated Tutorials

 References

 PDF Printing Version