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PHP Objects, Patterns, and Practice
SAMS Teach Yourself PHP SecOnd editiOn
in 24 Hours P
Dear Reader,
In recent years, PHP has embraced the object-oriented revolution, both in
terms of usage patterns and language features. Still, though, most books about H
object-oriented design focus on languages like Java and C++. But one of the nice
things about designing with objects is how concepts can travel among languages. In PHP Objects,
this book, I explore object-oriented programming and design from the standpoint
of a PHP programmer. P
I begin with an overview of PHP’s object-oriented features, introducing key
topics like class declaration, object instantiation, inheritance, and method
and property encapsulation. You’ll also learn about advanced topics including
static methods and properties, abstract classes, interfaces, exception handling, a O Patterns,
object cloning, and more. You’ll benefit from an extensive discussion of best n and
b
practices in object-oriented design too. d
The next part of this book is devoted to design patterns, a subject that naturally j
Pe
complements object orientation. I introduce pattern concepts and show you
how to implement several key patterns in your PHP applications, and I include rc
chapters on enterprise and database patterns. at Practice
In the last segment of this book, I introduce a number of great utilities that cs
help you document, manage, test, and build your PHP applications, including ,
t
Phing, PHPUnit2, PHPDocumentor, PEAR, and CVS. iP
I wrote PHP Objects, Patterns, and Practice to give you the kind of help I c
a
would have liked when I first discovered object-oriented programming and e
design patterns, since I learned a lot of lessons the hard way, in both code t
t
design and good project practice.
e
Matt Zandstra r
n Build powerful code by mastering PHP’s
s object-oriented enhancements, design
,
THE APRESS ROADMAP patterns, and essential development tools
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Matt Zandstra
SOURCE CODE ONLINE ISBN-13: 978-1-59059-909-9 an
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this print for content only—size & color not accurate spine = 0.9682" 512 page count

9098_FM.qxd 11/17/07 11:27 AM Page i
PHP Objects, Patterns,
and Practice
Second Edition
Matt Zandstra
9098_FM.qxd 11/17/07 11:27 AM Page ii
PHP Objects,Patterns,and Practice,Second Edition
Copyright © 2008 by Matt Zandstra
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ISBN-10 (pbk): 1-59059-909-8
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ISBN-10 (electronic): 1-4302-0466-4
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For Louise,who is the whole point
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Contents at a Glance
About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
About the Technical Reviewer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii
Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
Introduction to the First Edition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi
Introduction to the Second Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
PART 1 ■ ■ ■ Introduction
■ CHAPTER 1 PHP:Design and Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
PART 2 ■ ■ ■ Objects
■ CHAPTER 2 PHP and Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
■ CHAPTER 3 Object Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
■ CHAPTER 4 Advanced Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
■ CHAPTER 5 Object Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
■ CHAPTER 6 Objects and Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
PART 3 ■ ■ ■ Patterns
■ CHAPTER 7 What Are Design Patterns? Why Use Them? . . . . . . . . . . . . . . . . . . . 121
■ CHAPTER 8 Some Pattern Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
■ CHAPTER 9 Generating Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
■ CHAPTER 10 Patterns for Flexible Object Programming . . . . . . . . . . . . . . . . . . . . . 167
■ CHAPTER 11 Performing and Representing Tasks. . . . . . . . . . . . . . . . . . . . . . . . . . . 187
■ CHAPTER 12 Enterprise Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
■ CHAPTER 13 Database Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
iv
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PART 4 ■ ■ ■ Practice
■ CHAPTER 14 Good (and Bad) Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
■ CHAPTER 15 An Introduction to PEAR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
■ CHAPTER 16 Generating Documentation with phpDocumentor . . . . . . . . . . . . . . 353
■ CHAPTER 17 Version Control with CVS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
■ CHAPTER 18 Testing with PHPUnit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391
■ CHAPTER 19 Automated Build with Phing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413
PART 5 ■ ■ ■ Conclusion
■ CHAPTER 20 Objects,Patterns,Practice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435
PART 6 ■ ■ ■ Appendixes
■ APPENDIX A Bibliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447
■ APPENDIX B A Simple Parser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449
■ INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471
v
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Contents
About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
About the Technical Reviewer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii
Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
Introduction to the First Edition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi
Introduction to the Second Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
PART 1 ■ ■ ■ Introduction
■ CHAPTER 1 PHP: Design and Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
The Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
PHP and Other Languages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
About This Book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Practice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
What’s New in the Second Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
PART 2 ■ ■ ■ Objects
■ CHAPTER 2 PHP and Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
The Accidental Success of PHP Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
In the Beginning:PHP/FI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Syntactic Sugar:PHP 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
PHP 4 and the Quiet Revolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Change Embraced:PHP 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Into the Future:PHP 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Advocacy and Agnosticism:The Object Debate. . . . . . . . . . . . . . . . . . . . . . 15
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
vii
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viii ■ CONTENTS
■ CHAPTER 3 Object Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Classes and Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
A First Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
A First Object (or Two). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Setting Properties in a Class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Working with Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Creating a Constructor Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Arguments and Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Primitive Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Taking the Hint:Object Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
The Inheritance Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Working with Inheritance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Public,Private,and Protected:Managing Access to
Your Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
■ CHAPTER 4 Advanced Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Static Methods and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Constant Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Abstract Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Handling Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Exceptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Final Classes and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Working with Interceptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Defining Destructor Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Copying Objects with __clone() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Defining String Values for Your Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
■ CHAPTER 5 Object Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
PHP and Packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
PHP and Namespaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Include Paths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Autoload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77