Mastering Joomla! 1.5
Extension and Framework
Development
The Professional's Guide to Programming
Joomla!
James Kennard
BIRMINGHAM - MUMBAI
Mastering Joomla! 1.5 Extension and Framework
Development
The Professional's Guide to Programming Joomla!
Copyright © 2007 Packt Publishing
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However, Packt Publishing cannot guarantee the accuracy of this information.
First published: November 2007
Production Reference: 1311007
Published by Packt Publishing Ltd.
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ISBN 978-1-84719-282-0

James Kennard
is a computer programmer with a particular interest in web-based
services. His interests in Joomla! started as a result of an internal assignment at work
when he was tasked with identifying suitable web systems to host a number of
intranet and Internet applications.
James currently maintains one open-source Joomla! component, which has been
translated into over fteen languages. Examples of his work can be found on his
personal website:
www.webamoeba.co.uk
.
About the Reviewers
Joseph L. LeBlanc
started with computers at a very young age. His independent
education gave him the exibility to experiment and learn computer science. Joseph
holds a bachelor's degree in Management Information Systems from the Oral
Roberts University.
Joseph is currently a freelance Joomla! extension developer. He released a popular
component tutorial in May 2004, then later authored the book Learning Joomla! 1.5
Extension Development: Creating Modules, Components, and Plugins with PHP. Work
samples and open-source extensions are available at
www.jlleblanc.com
. In
addition to freelancing, he is a board member of the DC PHP Conference. He has
also worked as a programmer for a web communications rm in Washington, DC.
Riccardo Tacconi
works for an Italian company as a system administrator and
web developer using PHP, MySQL, and Oracle. He is an MCP and studies IT
part-time at the British Open University. His main interests are web development,
Windows and Linux administration, Robotics, and Java software development (JMF,
motion detection, CV, and distributed systems).

A Quick Lesson in Classes 27
Inheriting from JObject 28
Table of Contents
[
ii
]
Working with the Request 29
The Factory 30
The Session 31
Predefined Constants 32
Multilingual Support 34
UTF-8 String Handling 34
Coding Standards 36
phpDocumentor 37
Summary 39
Chapter 3: The Database 41
The Core Database 41
Extending the Database 42
Table Prefix 42
Schema Conventions 42
Common Fields 42
Schema Example 44
Dealing with Multilingual Requirements 45
Querying the Database 46
Writing Queries 46
Getting Results 47
loadResult( ) : string 48
loadResultArray( numinarray : int=0 ) : array 48
loadAssoc( ) : array 48
loadAssocList( key : string='' ) : array 49

Raw 91
Dealing with Component Configuration 93
Elements and Parameters 95
Extending JElement 96
Using Custom JElement Classes 98
Help Files 99
Routing 100
Packaging 102
XML Manifest File 103
SQL Install and Uninstall Files and Queries 110
Install and Uninstall Files 111
Summary 113
Chapter 5: Module Design 115
Setting Up a Sandbox 115
First Steps 116
Standalone Modules 117
Modules and Components Working Together 118
Frontend and Backend Module Display Positions 119
Module Settings (Parameters) 120
Helpers 121
Layouts (Templates) 124
Media 126
Translating 126
Packaging 127
XML Manifest File 127
Summary 131
Chapter 6: Plugin Design 133
Setting Up a Sandbox 134
Events 136
Listeners 138

User Parameters 178
The Session 184
The Browser 185
Assets 189
Summary 190
Chapter 8: Rendering Output 193
The joomla.html Library 193
Behavior 196
Email 200
Grid 200
Image 203
List 204
Menu 208
Select 209
Building Component HTML Layouts (Templates) 212
Iterative Templates 213
Table of Contents
[
v
]
Component Backend 214
Admin Form 215
Toolbar 216
Sub-Menu 222
Itemized Data 224
Pagination 224
Ordering 228
Filtering and Searching 231
Summary 241
Chapter 9: Customizing the Page 243

Table of Contents
[
vi
]
File Transfer Protocol 297
Web Services 299
Building a Web Service (XML-RPC Plugin) 301
Summary 309
Chapter 11: Error Handling and Security 311
Errors, Warnings, and Notices 312
Return Values 313
Customizing Error Handling 314
Dealing with CGI Request Data 315
Preprocessing CGI Data 315
Escaping and Encoding Data 317
Escaping and Quoting Database Data 318
Encode XHTML Data 319
Regular Expressions 320
Patterns 320
Matching 322
Replacing 323
Access Control 323
Menu Item Access Control 325
Extension Access Control 325
Attacks 327
How to Avoid Common Attacks 328
Using the Session Token 328
Code Injection 329
XSS (Cross Site Scripting) 331
File System Snooping 332

JModel 372
Properties 372
Constructors 372
Methods 372
JView 374
Properties 375
Constructors 375
Methods 375
JController 378
Properties 379
Constructors 379
Methods 379
JTable 383
Properties 383
Constructors 383
Methods 384
JError 388
Methods 388
JDocument 393
Properties 393
Constructors 393
Methods 394
JApplication 398
Properties 398
Constructors 399
Methods 399
JURI 407
Properties 407
Constructors 407
Methods 407

Methods 428
JRegistry 431
Properties 431
Constructors 431
Methods 431
JSession 434
Properties 434
Constructors 434
Methods 435
JRoute 438
Methods 438
JMenu 438
Properties 438
Constructors 439
Methods 439
JPathway 441
Properties 441
Methods 441
JDatabase 442
Properties 442
Constructors 443
Methods 443
Parameters (Core JElements) 452
Configuration 455
Index 459
Preface
This book will guide you through the complexities of implementing components,
modules, and plugins in Joomla! 1.5. It provides useful reference material that
explains many of the advanced design features and classes available in Joomla! 1.5.
Joomla! is one of the world's top open-source content management systems. The

Chapter 4 is about designing components. It starts with the structure and a basic
design of a component using the MVC design pattern. Then we learn conguring
the component and its various elements and parameters. The chapter nishes by
discussing component packaging and the various install and uninstall les.
Chapter 5 covers designing modules. It explains standalone modules, module
settings, frontend and backend modules, and modules and components working
together. Then we talk about using templates and packaging the modules.
Chapter 6 deals with designing plugins. It initially deals with listeners/observers
and then the various plugin groups like authentication, content editors, search, and
others. Then comes loading, translating, and using plugins as libraries. Finally it
deals with, plugin settings and how to package plugins.
Chapter 7 is all about designing extensions. Here, we start with helper classes then
cover building and using
getInstance()
methods. Then we cover the registry along
with saving and loading registry values. Towards the end of the chapter, we explain
the User, Session, Browser and the assets.
Chapter 8 explains ways to render output and how to maintain consistency
throughout. It starts with the
joomla.html
library and then continues to describe
how to build component HTML layouts. Then it discusses how to output the backend
of a component. The chapter ends with the details of itemized data and pagination.
Chapter 9 deals with customizing the page. We cover things like modifying the
document and translating, along with a brief explanation of using JavaScript effects
from the mootools library, which is included in Joomla!.
Chapter 10 explores some of the Joomla! APIs, specically in relation to web services.
We also discuss some of the more common web services and take a more in-depth
look at the Yahoo! Search API. The chapter nishes by describing how we can create
our own web services using plugins.

$user =& JFactory::getUser();
if ($user->guest)
{
// user is a guest (is not logged in)
}
New terms and important words are introduced in a bold-type font. Words that you
see on the screen, in menus or dialog boxes for example, appear in our text like this:
"In the System tab we must set Debug Language to Yes".
Warnings or important notes appear in a box like this.
Tips and tricks appear like this.
Preface
[
4
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5
]
Questions
You can contact us at
[email protected]
if you are having a problem with
some aspect of the book, and we will do our best to address it.

Introduction to Joomla!
This book is intended for use as a reference book for existing Joomla! developers.
It focuses on the Joomla! framework and how to utilize it to enhance and
standardize extensions.
Overview
Joomla! is a modular and extensible PHP MySQL CMS (Content Management
System). Joomla! is an open-source project, which is released under version 2 of the
GPL license. Joomla! has fast become one of the most popular open-source CMS, as is
proved by its numerous awards and massive online community.
One of the things that has made Joomla! so popular is the large number of freely and
commercially available extensions, which enable users to do far more than simply
manage content. This list details some common functions that extensions perform:
Banner Ads & Afliates
Calendars
Communication (Chat Rooms, Forums, Guest Books, Mailing Lists,
Newsletters)
Content & News (Blogs, eCards, News)
Documentation (Downloads, FAQs, Wikis)
eCommerce (Auctions, Shopping Carts)
Forms
Gallery & Multimedia
Intranet & Groupware

The creation of the Mambo Foundation created a rift in the Mambo Open Source
community. The creation of the Mambo Foundation was seen by many as an attempt
by Rice Studios to gain control of the Mambo Open Source project.
Not long after the Mambo Foundation was created, a group, consisting mainly of
the Mambo Open Source core developers, publicly announced that they intended to
abandon Mambo Open Source. The group formed a non-prot organization called
'Open Source Matters'.
Open Source Matters created the Joomla! project, a guaranteed 100% open-source
GPL project. The rst release of Joomla! (Joomla! 1.0) was very similar to the then
current release of Mambo, the majority of extensions at the time being compatible
with both.
Restraints within Joomla! 1.0 led to a complete re-think of how Joomla! should be
constructed. After a long development period, and two beta releases, Joomla! 1.5 was
released in mid 2007.
Joomla! 1.5 is extensively different to Joomla! 1.0 and Mambo. Joomla! 1.5 introduces
many new classes and implements a comprehensive framework. These changes have
lead to reduced compatibility between Joomla! and Mambo.
The most notable change, for most third-party extension developers, is the
introduction of the MVC (Model View Controller) design pattern in components.
These changes now mean that all third-party developers tend to develop for Joomla!
or Mambo, but not both.
Chapter 1
[
9
]
Requirements
To use Joomla! and develop new extensions there are a number of basic
requirements. This list details the minimum requirements:
MySQL 3.23 available at
http://www.mysql.com

There are three main types of extension: components, modules, and plugins.
There are also languages and templates, but these are solely designed to modify
page output, irrespective of the data being displayed. Although we will discuss the
use of translation les and templates, we will not explicitly cover these two extension
types in this book.
•
•
•
Introduction to Joomla!
[
10
]
Tools, sometimes referred to as extensions, are essentially any type of extension
that does not fall into the extension type categories just described. We will not be
discussing how to create tools in this book.
Extensions are distributed in archive les, which include an XML manifest le that
describes the extension. It is from the manifest le that Joomla! is able to determine
what type the extension is, what it is called, what les are included, and what
installation procedures are required.
Components
Components are undoubtedly the most fundamental Joomla! extensions. Whenever
Joomla! is invoked a component is always called upon. Unlike other extensions,
output created by a component is displayed in the main content area. Since
components are the most fundamental extension, they are also generally the
most complex.
One component of which all Joomla! administrators will be aware, is the content
component. This component is used to display articles, content categories, and
content sections.
In addition to outputting component data as part of an XHTML page, we can output
component data as Feeds, PDF, and RAW documents.