PHP Tutorials - Herong's Tutorial Examples

∟Introduction of Class and Object

∟What Is an Overloaded Property

This section describes what is an overloaded property - A class property that is not directly declared at all or not declared as publicly accessible, but it is provided indirectly through implementations of __set(), __get(), __isset(), and __unset() methods.

What Is an Overloaded Property? An overloaded property is a class property that is not directly declared at all or not declared as publicly accessible, but it is provided indirectly through implementations of __set(), __get(), __isset(), and __unset() methods.

In PHP, any class can implement the following special methods to support overloaded properties:

• __set($name, $value) - To be invoked when writing data to an inaccessible property, like "$object->name = $value".
• __get($name) - To be invoked when reading data from an inaccessible property, like "$value = $object->name".
• __isset($name) - To be invoked when testing the existence of an inaccessible property, like "isset($object->name)";
• __unset($name) - To be invoked when removing an inaccessible property from the object, like "unset($object->name)";

For example, the following tutorial example provides class "MyPropertyBag" that shows how to use __set(), __get(), __isset(), and __unset() methods to support overloaded properties.

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

class MyPropertyBag {
   public $size = 0;
   private $propertyBag = array();
   public function __set($name, $value) {
      $this->propertyBag[$name] = $value;
      $this->size = count($this->propertyBag);
   }
   public function __get($name) {
      if (array_key_exists($name, $this->propertyBag)) {
         return $this->propertyBag[$name];
      } else {
         return "__undefined__";
      }
   }
   public function __isset($name) {
      return isset($this->propertyBag[$name]);
   }
   public function __unset($name) {
      unset($this->propertyBag[$name]);
      $this->size = count($this->propertyBag);
   }
}

  $object = new MyPropertyBag();
  $object->type = "Book";
  $object->title = "PHP Tutorials";

  echo "MyPropertyBag object: \n";
  echo "   Size: ". $object->size ."\n";
  echo "   Type: ". $object->type ."\n";
  echo "   Title: ". $object->title ."\n";
  echo "   Author: ". $object->author ."\n";
  echo "   isset(Author): ". isset($object->author) ."\n";
?>

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

herong> \php\php MyPropertyBag.php

MyPropertyBag object:
   Size: 2
   Type: Book
   Title: PHP Tutorials
   Author: __undefined__
   isset(Author):

Table of Contents

 About This Book

 Introduction and Installation of PHP

 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

 Interface with Operating System

►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

 Managing File Upload

 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

 Parsing and Managing HTML Documents

 Configuring and Sending Out Emails

 Image and Picture Processing

 Managing ZIP Archive Files

 Managing PHP Engine and Modules on macOS

 Managing PHP Engine and Modules on CentOS

 Archived Tutorials

 References

 Full Version in PDF/EPUB

What Is an Overloaded Property - Updated in 2023, by Herong Yang