PHP Objects, Patterns, and Practice- P1

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PHP Objects, Patterns, and Practice- P1: This book takes you beyond the PHP basics to the enterprise development practices used by professional programmers. Updated for PHP 5.3 with new sections on closures, namespaces, and continuous integration, this edition will teach you about object features such as abstract classes, reflection, interfaces, and error handling. You’ll also discover object tools to help you learn more about your classes, objects, and methods.

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THE EXPERT’S VOICE ® IN OPEN SOURCE PHP Objects, Patterns, and Practice Build powerful code by mastering PHP’s object-oriented enhancements, design patterns, and essential development tools THIRD EDITION Matt Zandstra
PHP Objects, Patterns, and Practice Third Edition ■■■ Matt Zandstra i
PHP Objects, Patterns, and Practice, Third Edition Copyright © 2010 by Matt Zandstra All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher. ISBN-13 (pbk): 978-1-4302-2925-4 ISBN-13 (electronic): 978-1-4302-2926-1 Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1 Trademarked names may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, we use the names only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. President and Publisher: Paul Manning Lead Editor: Michelle Lowman, Matt Wade Technical Reviewer: Wes Hunt Editorial Board: Clay Andres, Steve Anglin, Mark Beckner, Ewan Buckingham, Gary Cornell, Jonathan Gennick, Jonathan Hassell, Michelle Lowman, Matthew Moodie, Duncan Parkes, Jeffrey Pepper, Frank Pohlmann, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft, Matt Wade, Tom Welsh Coordinating Editor: Jim Markham Copy Editor: Tracy Brown Collins Compositor: MacPS, LLC Indexer: Toma Mulligan Artist: April Milne Cover Designer: Anna Ischenko Distributed to the book trade worldwide by Springer-Verlag New York, Inc., 233 Spring Street, 6th Floor, New York, NY 10013. Phone 1-800-SPRINGER, fax 201-348-4505, e-mail orders-ny@springer-sbm.com, or visit www.springeronline.com. For information on translations, please e-mail info@apress.com, or visit www.apress.com. Apress and friends of ED books may be purchased in bulk for academic, corporate, or promotional use. eBook versions and licenses are also available for most titles. For more information, reference our Special Bulk Sales–eBook Licensing web page at www.apress.com/info/bulksales. The information in this book is distributed on an “as is” basis, without warranty. Although every precaution has been taken in the preparation of this work, neither the author(s) nor Apress shall have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information contained in this work. The source code for this book is available to readers at www.apress.com. You will need to answer questions pertaining to this book in order to successfully download the code. ii
Contents at a Glance ■Contents at a Glance.......................................................................................................................iii ■Contents .......................................................................................................................................... v ■About the Author ......................................................................................................................... xvii ■About the Technical Reviewer .................................................................................................... xviii ■Acknowledgments ........................................................................................................................ xix ■Introduction to the Third Edition ................................................................................................... xx Part 1: Introduction.............................................................................................................................1 ■Chapter 1: PHP: Design and Management .......................................................................................3 Part 2: Objects ....................................................................................................................................9 ■Chapter 2: PHP and Objects...........................................................................................................11 ■Chapter 3: Object Basics ...............................................................................................................15 ■Chapter 4: Advanced Features.......................................................................................................41 ■Chapter 5: Object Tools..................................................................................................................71 ■Chapter 6: Objects and Design ......................................................................................................99 Part 3: Patterns...............................................................................................................................121 ■Chapter 7: What Are Design Patterns? Why Use Them? ..............................................................123 ■Chapter 8: Some Pattern Principles ............................................................................................131 ■Chapter 9: Generating Objects.....................................................................................................145 ■Chapter 10: Patterns for Flexible Object Programming...............................................................169 ■Chapter 11: Performing and Representing Tasks........................................................................189 ■Chapter 12: Enterprise Patterns ..................................................................................................221 ■Chapter 13: Database Patterns....................................................................................................275 Part 4: Practice...............................................................................................................................315 ■Chapter 14: Good (and Bad) Practice ..........................................................................................317 ■Chapter 15: An Introduction to PEAR and Pyrus..........................................................................323 ■Chapter 16: Generating Documentation with phpDocumentor ....................................................347 ■Chapter 17: Version Control with Subversion..............................................................................361 ■Chapter 18: Testing with PHPUnit................................................................................................379 ■Chapter 19: Automated Build with Phing ....................................................................................407 ■Chapter 20: Continuous Integration.............................................................................................427 Part 5: Conclusion...........................................................................................................................451 ■Chapter 21: Objects, Patterns, Practice ......................................................................................453 ■Appendix A: Bibliography ............................................................................................................463 ■Appendix B: A Simple Parser.......................................................................................................467 ■Index............................................................................................................................................219 iii
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Contents ■Contents at a Glance ............................................................................................iii ■Contents ................................................................................................................v ■About the Author ............................................................................................... xvii ■About the Technical Reviewer.......................................................................... xviii ■Acknowledgments.............................................................................................. xix ■Introduction to the Third Edition ......................................................................... xx Part 1: Introduction ..................................................................................................1 ■Chapter 1: PHP: Design and Management.............................................................3 The Problem.................................................................................................................... 3 PHP and Other Languages .............................................................................................. 4 About This Book .............................................................................................................. 5 Objects ...................................................................................................................................................6 Patterns..................................................................................................................................................6 Practice ..................................................................................................................................................6 What’s New in the Third Edition.............................................................................................................7 Summary......................................................................................................................... 7 Part 2: Objects..........................................................................................................9 ■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 v
■ CONTENTS Change Embraced: PHP 5 ....................................................................................................................13 Into the Future .............................................................................................................. 14 Advocacy and Agnosticism: The Object Debate............................................................ 14 Summary....................................................................................................................... 14 ■Chapter 3: Object Basics .....................................................................................15 Classes and Objects...................................................................................................... 15 A First Class .........................................................................................................................................15 A First Object (or Two) .........................................................................................................................16 Setting Properties in a Class........................................................................................ 17 Working with Methods .................................................................................................. 19 Creating a Constructor Method ............................................................................................................21 Arguments and Types ................................................................................................... 22 Primitive Types ....................................................................................................................................22 Taking the Hint: Object Types ..............................................................................................................25 Inheritance .................................................................................................................... 27 The Inheritance Problem......................................................................................................................27 Working with Inheritance.....................................................................................................................31 Public, Private, and Protected: Managing Access to Your Classes ......................................................35 Summary....................................................................................................................... 39 ■Chapter 4: Advanced Features ............................................................................41 Static Methods and Properties...................................................................................... 41 Constant Properties ...................................................................................................... 44 Abstract Classes ........................................................................................................... 45 Interfaces ...................................................................................................................... 47 Late Static Bindings: The static Keyword.................................................................. 48 Handling Errors ............................................................................................................. 51 Exceptions............................................................................................................................................52 Final Classes and Methods ........................................................................................... 57 Working with Interceptors ............................................................................................ 58 Defining Destructor Methods ........................................................................................ 62 vi
■ CONTENTS Copying Objects with __clone() .................................................................................... 63 Defining String Values for Your Objects........................................................................ 65 Callbacks, Anonymous Functions and Closures ........................................................... 66 Summary....................................................................................................................... 70 ■Chapter 5: Object Tools .......................................................................................71 PHP and Packages ........................................................................................................ 71 PHP Packages and Namespaces..........................................................................................................71 Autoload ...............................................................................................................................................80 The Class and Object Functions.................................................................................... 81 Looking for Classes..............................................................................................................................82 Learning About an Object or Class.......................................................................................................83 Learning About Methods ......................................................................................................................84 Learning About Properties ...................................................................................................................85 Learning About Inheritance..................................................................................................................85 Method Invocation................................................................................................................................86 The Reflection API......................................................................................................... 87 Getting Started .....................................................................................................................................87 Time to Roll Up Your Sleeves ...............................................................................................................88 Examining a Class ..............................................................................................................................90 Examining Methods..............................................................................................................................91 Examining Method Arguments.............................................................................................................93 Using the Reflection API.......................................................................................................................94 Summary....................................................................................................................... 97 ■Chapter 6: Objects and Design ............................................................................99 Defining Code Design.................................................................................................... 99 Object-Oriented and Procedural Programming........................................................... 100 Responsibility.....................................................................................................................................103 Cohesion ............................................................................................................................................104 Coupling .............................................................................................................................................104 Orthogonality......................................................................................................................................104 Choosing Your Classes................................................................................................ 105 vii
■ CONTENTS Polymorphism ............................................................................................................. 106 Encapsulation ............................................................................................................. 107 Forget How to Do It ..................................................................................................... 108 Four Signposts ............................................................................................................ 109 Code Duplication ................................................................................................................................109 The Class Who Knew Too Much .........................................................................................................109 The Jack of All Trades........................................................................................................................109 Conditional Statements......................................................................................................................110 The UML ...................................................................................................................... 110 Class Diagrams ..................................................................................................................................110 Sequence Diagrams...........................................................................................................................117 Summary..................................................................................................................... 119 Part 3: Patterns ....................................................................................................121 ■Chapter 7: What Are Design Patterns? Why Use Them?....................................123 What Are Design Patterns? ......................................................................................... 123 A Design Pattern Overview ......................................................................................... 125 Name..................................................................................................................................................125 The Problem.......................................................................................................................................125 The Solution .......................................................................................................................................126 Consequences....................................................................................................................................126 The Gang of Four Format ............................................................................................ 126 Why Use Design Patterns?.......................................................................................... 127 A Design Pattern Defines a Problem ..................................................................................................127 A Design Pattern Defines a Solution ..................................................................................................127 Design Patterns Are Language Independent......................................................................................127 Patterns Define a Vocabulary.............................................................................................................127 Patterns Are Tried and Tested ...........................................................................................................128 Patterns Are Designed for Collaboration............................................................................................128 Design Patterns Promote Good Design ..............................................................................................128 PHP and Design Patterns ............................................................................................ 129 Summary..................................................................................................................... 129 viii
■ CONTENTS ■Chapter 8: Some Pattern Principles ..................................................................131 The Pattern Revelation................................................................................................ 131 Composition and Inheritance ...................................................................................... 132 The Problem.......................................................................................................................................132 Using Composition .............................................................................................................................135 Decoupling .................................................................................................................. 137 The Problem.......................................................................................................................................137 Loosening Your Coupling ...................................................................................................................139 Code to an Interface, Not to an Implementation ......................................................... 141 The Concept That Varies ............................................................................................. 142 Patternitis.................................................................................................................... 143 The Patterns................................................................................................................ 143 Patterns for Generating Objects.........................................................................................................143 Patterns for Organizing Objects and Classes .....................................................................................143 Task-Oriented Patterns ......................................................................................................................143 Enterprise Patterns ............................................................................................................................144 Database Patterns..............................................................................................................................144 Summary..................................................................................................................... 144 ■Chapter 9: Generating Objects ..........................................................................145 Problems and Solutions in Generating Objects........................................................... 145 The Singleton Pattern ................................................................................................. 149 The Problem.......................................................................................................................................149 Implementation ..................................................................................................................................150 Consequences....................................................................................................................................152 Factory Method Pattern .............................................................................................. 152 The Problem.......................................................................................................................................153 Implementation ..................................................................................................................................155 Consequences....................................................................................................................................157 Abstract Factory Pattern ............................................................................................. 157 The Problem.......................................................................................................................................158 Implementation ..................................................................................................................................159 ix
■ CONTENTS Consequences....................................................................................................................................161 Prototype............................................................................................................................................162 The Problem.......................................................................................................................................163 Implementation ..................................................................................................................................163 But That’s Cheating! ................................................................................................... 166 Summary..................................................................................................................... 167 ■Chapter 10: Patterns for Flexible Object Programming ....................................169 Structuring Classes to Allow Flexible Objects............................................................. 169 The Composite Pattern................................................................................................ 169 The Problem.......................................................................................................................................170 Implementation ..................................................................................................................................172 Consequences....................................................................................................................................175 Composite in Summary......................................................................................................................178 The Decorator Pattern................................................................................................. 179 The Problem.......................................................................................................................................179 Implementation ..................................................................................................................................181 Consequences....................................................................................................................................185 The Facade Pattern..................................................................................................... 185 The Problem.......................................................................................................................................185 Implementation ..................................................................................................................................186 Consequences....................................................................................................................................187 Summary..................................................................................................................... 187 ■Chapter 11: Performing and Representing Tasks .............................................189 The Interpreter Pattern................................................................................................ 189 The Problem.......................................................................................................................................189 Implementation ..................................................................................................................................190 Interpreter Issues...............................................................................................................................197 The Strategy Pattern ................................................................................................... 198 The Problem.......................................................................................................................................198 Implementation ..................................................................................................................................199 The Observer Pattern .................................................................................................. 202 x
■ CONTENTS Implementation ..................................................................................................................................204 The Visitor Pattern ...................................................................................................... 210 The Problem.......................................................................................................................................210 Implementation ..................................................................................................................................211 Visitor Issues......................................................................................................................................215 The Command Pattern ................................................................................................ 216 The Problem.......................................................................................................................................216 Implementation ..................................................................................................................................216 Summary..................................................................................................................... 220 ■Chapter 12: Enterprise Patterns........................................................................221 Architecture Overview................................................................................................. 221 The Patterns.......................................................................................................................................222 Applications and Layers.....................................................................................................................222 Cheating Before We Start............................................................................................ 225 Registry..............................................................................................................................................225 Implementation ..................................................................................................................................226 The Presentation Layer ............................................................................................... 235 Front Controller ..................................................................................................................................235 Application Controller.........................................................................................................................245 Page Controller ..................................................................................................................................257 Template View and View Helper ........................................................................................................262 The Business Logic Layer ........................................................................................... 264 Transaction Script..............................................................................................................................265 Domain Model ....................................................................................................................................269 Summary..................................................................................................................... 273 ■Chapter 13: Database Patterns .........................................................................275 The Data Layer ............................................................................................................ 275 Data Mapper ............................................................................................................... 275 The Problem.......................................................................................................................................276 Implementation ..................................................................................................................................276 Consequences....................................................................................................................................287 xi
■ CONTENTS Identity Map ................................................................................................................ 288 The Problem.......................................................................................................................................288 Implementation ..................................................................................................................................289 Consequences....................................................................................................................................291 Unit of Work ................................................................................................................ 291 The Problem.......................................................................................................................................292 Implementation ..................................................................................................................................292 Consequences....................................................................................................................................296 Lazy Load ...........................................................................................................................................296 The Problem.......................................................................................................................................296 Implementation ..................................................................................................................................297 Consequences....................................................................................................................................298 Domain Object Factory................................................................................................ 298 The Problem.......................................................................................................................................298 Implementation ..................................................................................................................................299 Consequences....................................................................................................................................300 The Identity Object ...................................................................................................... 301 The Problem.......................................................................................................................................301 Implementation ..................................................................................................................................302 Consequences....................................................................................................................................307 The Selection Factory and Update Factory Patterns ................................................... 307 The Problem.......................................................................................................................................307 Implementation ..................................................................................................................................307 Consequences....................................................................................................................................311 What’s Left of Data Mapper Now? .............................................................................. 311 Summary..................................................................................................................... 313 Part 4: Practice ....................................................................................................315 ■Chapter 14: Good (and Bad) Practice ................................................................317 Beyond Code ............................................................................................................... 317 Borrowing a Wheel..................................................................................................... 317 Playing Nice ................................................................................................................ 319 xii
■ CONTENTS Giving Your Code Wings .............................................................................................. 319 Documentation............................................................................................................ 320 Testing ........................................................................................................................ 321 Continuous Integration................................................................................................ 322 Summary..................................................................................................................... 322 ■Chapter 15: An Introduction to PEAR and Pyrus ...............................................323 What Is PEAR?............................................................................................................. 323 Phar Out with Pyrus .................................................................................................... 324 Installing a Package................................................................................................... 326 PEAR Channels...................................................................................................................................327 Using a PEAR Package................................................................................................ 329 Handling PEAR Errors.........................................................................................................................331 Creating Your Own PEAR Package .............................................................................. 334 package.xml.......................................................................................................................................334 Package Elements..............................................................................................................................334 The contents Element .....................................................................................................................336 Dependencies ....................................................................................................................................339 Tweaking Installation with phprelease ...........................................................................................340 Preparing a Package for Shipment ....................................................................................................341 Setting Up Your Own Channel ............................................................................................................341 Summary..................................................................................................................... 346 ■Chapter 16: Generating Documentation with phpDocumentor..........................347 Why Document?.......................................................................................................... 347 Installation .................................................................................................................. 348 Generating Documentation ......................................................................................... 349 DocBlock Comments................................................................................................... 350 Documenting Classes ................................................................................................. 352 File-Level Documentation ........................................................................................... 353 Documenting Properties ............................................................................................. 353 Documenting Methods................................................................................................ 355 xiii
■ CONTENTS Creating Links in Documentation................................................................................ 356 Summary..................................................................................................................... 359 ■Chapter 17: Version Control with Subversion ...................................................361 Why Use Version Control?........................................................................................... 361 Getting Subversion...................................................................................................... 362 Configuring a Subversion Repository.......................................................................... 363 Creating a Repository.........................................................................................................................363 Beginning a Project..................................................................................................... 364 Updating and Committing ........................................................................................... 368 Adding and Removing Files and Directories ............................................................... 371 Adding a File ......................................................................................................................................371 Removing a File .................................................................................................................................372 Adding a Directory .............................................................................................................................372 Removing Directories.........................................................................................................................373 Tagging and Exporting a Release ............................................................................... 373 Tagging a Project ...............................................................................................................................373 Exporting a Project.............................................................................................................................374 Branching a Project..................................................................................................... 374 Summary..................................................................................................................... 378 ■Chapter 18: Testing with PHPUnit .....................................................................379 Functional Tests and Unit Tests.................................................................................. 379 Testing by Hand .......................................................................................................... 380 Introducing PHPUnit .................................................................................................... 382 Creating a Test Case ..........................................................................................................................382 Assertion Methods .............................................................................................................................383 Testing Exceptions .............................................................................................................................384 Running Test Suites ...........................................................................................................................385 Constraints.........................................................................................................................................386 Mocks and Stubs ...............................................................................................................................388 Tests Succeed When They Fail ..........................................................................................................391 xiv
■ CONTENTS Writing Web Tests....................................................................................................... 394 Refactoring a Web Application for Testing.........................................................................................394 Simple Web Testing ...........................................................................................................................397 Introducing Selenium .........................................................................................................................398 A Note of Caution ........................................................................................................ 403 Summary..................................................................................................................... 405 ■Chapter 19: Automated Build with Phing ..........................................................407 What Is Phing? ............................................................................................................ 407 Getting and Installing Phing ........................................................................................ 408 Composing the Build Document.................................................................................. 408 Targets ...............................................................................................................................................410 Properties...........................................................................................................................................412 Types..................................................................................................................................................416 Tasks..................................................................................................................................................421 Summary..................................................................................................................... 425 ■Chapter 20: Continuous Integration ..................................................................427 What Is Continuous Integration? ................................................................................. 427 Preparing a Project for CI...................................................................................................................428 CruiseControl and phpUnderControl............................................................................ 436 Installing CruiseControl......................................................................................................................436 Installing phpUnderControl.................................................................................................................438 Installing Your Project ........................................................................................................................440 Summary..................................................................................................................... 450 Part 5: Conclusion ................................................................................................451 ■Chapter 21: Objects, Patterns, Practice ............................................................453 Objects ........................................................................................................................ 453 Choice ................................................................................................................................................454 Encapsulation and Delegation............................................................................................................454 Decoupling .........................................................................................................................................454 Reusability .........................................................................................................................................455 Aesthetics ..........................................................................................................................................455 xv
■ CONTENTS Patterns....................................................................................................................... 455 What Patterns Buy Us ........................................................................................................................456 Patterns and Principles of Design ......................................................................................................456 Practice....................................................................................................................... 458 Testing ...............................................................................................................................................459 Documentation...................................................................................................................................459 Version Control...................................................................................................................................459 Automated Build.................................................................................................................................459 Continuous Integration.......................................................................................................................460 What I Missed ....................................................................................................................................460 Summary..................................................................................................................... 460 ■Appendix A: Bibliography..................................................................................463 Books .......................................................................................................................... 463 Articles........................................................................................................................ 464 Sites ............................................................................................................................ 464 ■Appendix B: A Simple Parser ............................................................................467 The Scanner................................................................................................................ 467 The Parser................................................................................................................... 474 ■Index .................................................................................................................487 xvi
■ CONTENTS About the Author ■ Matt Zandstra has worked as a web programmer, consultant, and writer for over a decade. He is a senior developer at Yahoo, and a freelance coder and writer. Matt is the author of Teach Yourself PHP in 24 Hours (SAMS) and a contributor to DHTML Unleashed (SAMS). He has written articles for Linux Magazine, Zend.com, IBM DeveloperWorks, and php|architect Magazine, among others. He works primarily with PHP and Java, designing and building web and command-line applications. Matt lives in Liverpool with his wife, Louise, and two children, Holly and Jake. xvii
■ CONTENTS About the Technical Reviewer ■ Wes Hunt is a web-application developer and consultant at 4th Dimension Development, which builds web solutions for organizations from small to the enterprise level. For over a decade, he has used Java and PHP to deliver everything plus the kitchen sink for clients. His latest passion is leveraging Flex with a PHP back-end to produce RIAs for clients. Wes uses development patterns and best practices in order to spend more time enjoying the outdoors near his home in Montana. xviii