PHP Tutorials - Herong's Tutorial Examples - v5.17, by Herong Yang
What Is a Constructor
This section describes what is a constructor - a special method to be invoked automatically when a new object is created from a class. The main purpose of the constructor is to provide initial values to object properties.
What Is a Constructor? A constructor is a special method to be invoked automatically when a new object is created from a class. The main purpose of the constructor is to provide initial values to object properties.
In PHP, the constructor method must be named as "__construct()". For example, the following class provides a constructor to initialize two properties of the new object:
<?php /* MyMessage.php #- Copyright 2015 (c) HerongYang.com. All Rights Reserved. */ class MyMessage { public $text; public $length; function __construct($t) { $this->text = $t; $this->length = strlen($t); } public function show() { echo $this->text . "\n"; echo "Number of bytes in the message: " . $this->length . "\n"; } } $msg = new MyMessage("Hello there!"); $msg->show(); ?>
Notice that:
If you run the above tutorial example, you will get:
herong> \php\php MyMessage.php Hello there! Number of bytes in the message: 12
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