PHP Tutorials - Herong's Tutorial Examples - v5.17, by Herong Yang
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:
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
Introduction and Installation of PHP
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
Interface with Operating System
►Introduction of Class and Object
What Is a Superclass and a Subclass
►What Is an Overloaded Property
What Is Object Property Iteration
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
Parsing and Managing HTML Documents
Configuring and Sending Out Emails
Managing PHP Engine and Modules on macOS