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PHP is a powerful yet easy-to-use tool for creating dynamic webcontent The perfect language for projects great and small, PHP

is used by Yahoo!, millions of personal home pages, and

everything in-between Best of all, PHP is open source and runs

on Unix, Windows, and Mac OS X

oriented programming, an integrated suite of XML tools, an all-new MySQL extension, web services with SOAP and REST, andhundreds of other improvements

The latest version, PHP 5, contains robust support for object-There are so many updates and new features, it's difficult to get

a handle on all the changes Documentation is scarce,

scattered, and rarely in-depth This book steadily guides youfrom the world of PHP 4 to PHP 5, covering what's completelynew, what's received an overhaul, and what's just slightly

different enough to slip you up

perfectly under PHP 5 That's why Upgrading to PHP 5 provides you with detailed side-by-side comparisons of PHP 4 and PHP 5

Finally, it provides an address book program This concrete

example combines the new features of PHP 5, demonstratingtheir usefulness in the context of a complete application Theaddress book shows you exactly how PHP 5 makes it faster andeasier to develop more powerful and flexible web applications

This book is not for people new to PHP If you're looking to learnthe language, check out these three excellent alternatives:

1 Learning PHP 5, by David Sklar This book provides a

gentle introduction to PHP for web designers and

other nontechnical people familiar with HTML and the Web, but not with programming and databases.

Programming PHP, by Rasmus Lerdorf and Kevin Tatroe Co-authored by the creator of PHP, Programming PHP is aimed at

anyone looking to learn PHP An exhaustive reference, this bookcovers all aspects of PHP, from basic concepts to advanced

techniques

Web Database Applications with PHP and MySQL, by Hugh

E.Williams and David Lane If you're comfortable programmingbut have only just started using SQL, this book teaches you

This book is divided into 10 chapters and 3 appendixes Thematerial in the first half of this book covers vital components ofeveryday web programming: object-oriented programming,MySQL, SQLite, and XML It's hard to use PHP 5 without them.Specifically:

extensions are all extremely useful for solving specific tasks.The more you program in PHP 5, the more you'll find yourselfintegrating these features into your code

Chapter 6, Iterators and SPL, shows how iterators and SPL

let you loop through directories, database queries, and XMLdocuments

to integrate PHP 5 into your existing web server and PHP 4setup

The official PHP Manual contains thousands of pages

covering all aspects of PHP It's an invaluable resource forlooking up functions

PHP mailing lists (http://www.php.net/mailing-lists.php)

Discuss PHP on the PHP mailing lists Don't be shy, there's alist for every topic: programming, databases, and even

PEAR (http://pear.php.net/)

Don't reimplement the wheel, download it from PEAR

PEARthe PHP Extension and Application RepositorycontainsPHP classes that simplify forms processing, provide a

database abstraction layer, generate class documentation,and solve hundreds of other tasks

PECL (http://pecl.php.net/)

PECL is PEAR's sister PECLthe PHP Extension CommunityLibraryis a collection of PHP extensions written in C They'rejust like the bundled PHP extensions, except they're

These books are all helpful problem-solving guides and

references Most of the books in the list are web-specific, andthe top six books are my favorite PHP and MySQL texts

The following programming and typesetting conventions areused in this book

Programming Conventions

The <?php and ?> opening and closing markers that begin andend a PHP program are generally omitted from examples in thisbook, except in examples where the body of the code includes

an opening or closing marker

The examples in this book were written to run under PHP 5 onboth Unix and Windows, except where noted in the text

At the time this book went to press, the latest available version

of PHP 5 was Release Candidate 3 (RC3) Also, MySQL 4.1 was

in beta It is possible that some changes may occur betweenRC3 and the final release Please check the online errata at

http://www.oreilly.com/catalog/upgradephp5/errata/ for anylast-minute updates

Typesetting Conventions

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, fileextensions, pathnames, and directories

Indicates commands, options, switches, variables,

attributes, keys, functions, types, classes, namespaces,methods, modules, properties, parameters, values, objects,events, event handlers, XML tags, HTML tags, macros, thecontents of files, or the output from commands

This book is here to help you get your job done In general, youmay use the code in this book in your programs and

documentation You do not need to contact us for permissionunless you're reproducing a significant portion of the code Forexample, writing a program that uses several chunks of codefrom this book does not require permission Selling or

distributing a CD-ROM of examples from O'Reilly books does

require permission Answering a question by citing this bookand quoting example code does not require permission

Incorporating a significant amount of example code from this

book into your product's documentation does require

permission

We appreciate, but do not require, attribution An attributionusually includes the title, author, publisher, and ISBN For

example: "Upgrading to PHP 5, by Adam Trachtenberg.

Copyright 2004 O'Reilly Media, Inc., 0-596-00636-5."

If you feel your use of code examples falls outside fair use orthe permission given here, feel free to contact us at

permissions@oreilly.com

Please address comments and questions concerning this book tothe publisher:

http://www.oreilly.com/catalog/upgradephp5/

To comment or ask technical questions about this book, sendemail to:

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For more information about our books, conferences, ResourceCenters, and the O'Reilly Network, see our web site at:

http://www.oreilly.com/

there's not a bozo in the bunch.

Genevieve d'Entremont prepared this book for productionand repaired my prose

chromatic published my PHP articles on ONLamp.com

A cornered Andy Oram and Bruce Epstein graciously

provided editorial guidance and support one late night atFOO Camp

Rob Romano transformed my crayon sketches into works ofart

Betsy Waliszewski got the word out early and often

However, two people contributed more messages to my inboxthan the others combined: Tatiana Diaz and Nat Torkington

I have no idea how Tatiana Diaz put up with my all-too-oftenclaims of "Oh sure, I can make that deadline," without reachingthrough the Internet and strangling me Without her gentle

prodding, Upgrading to PHP 5 wouldn't be available until PHP 6.

Nat Torkington is a great editor He gave me a push when I gotstuck and helped me reframe chapters when they became

misaligned He even lets me make Perl 6 jokes at his expense Ipay him the greatest compliment I can: this book would be farless helpful without him

Thanks to my family and friends for their support and

encouragement

Extra special thanks go to Elizabeth Hondl, my beautiful

princess and talking frog

PHP 4 is a wildly popular web programming language Web

servers on over 15,000,000 domains support PHP PHP is themost popular Apache module by almost a 2-to-1 margin But ifPHP's so great, why do we need PHP 5?

Well, PHP 4 isn't perfect While it makes developing web

applications quick and easy, it's occasionally weighted down byits legacy baggage This makes tackling some problems

MySQL

XML

These items have all been completely rewritten, turning themfrom limitations into star attractions While these changes alonewarrant a new version of PHP, PHP 5 also provides:

SQLite for an embedded database

Iterators

Streams

SOAP

Some of these features, such as iterators and exceptions, areavailable only due to fundamental changes in PHP's core

Others, such as streams and SQLite, are PHP 4.3 features thathave matured into prime-time use in PHP 5

This book shows you how to take advantage of these new

features in your applications Additionally, it places a specialemphasis on not just telling you what's new, but showing youhow and why it's new

Whenever possible, there's a direct comparison between thePHP 4 method of solving a task and the PHP 5 solution The PHP

5 way is frequently shorter, more elegant, and provides youwith greater flexibility The before-and-after examples

demonstrate in clear code what's better about PHP 5 and

provide you with concrete examples to ease the transition fromPHP 4 to PHP 5

This chapter serves as a dual introduction to both PHP 5 and

Upgrading to PHP 5 It begins with a brief history of PHP that

provides the motivation behind PHP 5 The next section

provides a short description of all the major new features ofPHP 5 and, at the same time, explains how the book is

organized This chapter ends with a discussion of how to installand configure PHP 5

To understand why PHP 5 came to exist, it's necessary to

quickly review the evolution of PHP as a language

When Rasmus Lerdorf created PHP back in 1995, it wasn't evencalled PHPhis Personal Home Page/Forms Interpreter languagewas known as PHP/FI At the time, PHP/FI's main focus wassolving small-time web tasks: guest books, hit counters, andbasic forms processing Its major benefit was its simplicity;PHP/FI made it easy to handle all the messy tasks thrown at aweb developer Additionally, it's C-like syntax was already

understood by many programmers

Over the next two years, PHP/FI gradually grew in popularity.However, by 1997, PHP/FI was already showing its age As theInternet gathered steam, programmers began to create morecomplex applications, such as e-commerce shopping carts

PHP/FI's quirks and limitations hindered development It wastoo slow and was missing some basic features, such as for andforeach loops

These problems caused Zeev Suraski and Andi Gutmans, ofZend fame, to begin work on a new version of PHP/FI This

version, which became PHP 3, solved many difficulties faced byPHP/FI developers while remaining true to the essential nature

of PHP/FI

In particular, PHP 3 was faster and more efficient than PHP/FI.The new parser also provided the opportunity to iron out somelanguage oddities, making PHP more consistent PHP 3's othermajor advance was an easy-to-use extension API Developersfrom all over contributed extensions to PHP, effectively turningPHP from a programming language into an entire web

development environment

introduced a very simplistic object-oriented syntax Originallythe result of a weekend hack, developers flocked to objects,much to the surprise of Zeev and Andi Unfortunately, PHP 3was ill-equipped to provide all the object-oriented features

While PHP 4 provided yet another burst of power, its secondaryobjective was backward compatibility There was a strong

emphasis on not breaking PHP 3 scripts under PHP 4 As a

result, beefing up the core language was not a main focus ofPHP 4 PHP 4 was released in May 2000, almost two years afterPHP 3

A lot has happened over the last four years Perl may be the

"duct tape of the Internet," but PHP is the real glue that holdsthe Web together However, PHP still faces challenges The

problems of performance and flexibility have long been

conquered, but now PHP is under attack from the twin foes ofJava and C#

Over the past 10 years, Java and C# have introduced advancedobject-oriented programming concepts to web development Yet

in many ways, despite all the improvements, PHP 4.3 is still thesame procedural language that Rasmus wrote a decade ago.PHP 5 finally grants developers their wish, providing a full set ofobject-oriented features

These features, which are discussed in Chapter 2, allow

developers to more easily develop large-scale applications

without resorting to the cumbersome workarounds necessary inPHP 4 They also let you write cleaner code that's less error-

prone and more maintainable.

Better object-oriented features aren't the only new features ofPHP 5 Many extensions have been rewritten to take advantage

of PHP 5's new capabilities, and many new extensions have

been added to the distribution

1.2.1 MySQL

The MySQL database is PHP's partner in crime Many developerspower their web sites with MySQL, yet PHP's original MySQLextension dates back to the days of PHP/FI It's showing its

age

In retrospect, some design decisions for the MySQL extensionweren't the best solution after all Also, the latest versions ofMySQL, 4.1 and 5.0, introduce many new features, some ofwhich require significant changes to the extension

As a result, PHP 5 comes with a completely new and improvedMySQL extension Dubbed MySQLi, for the MySQL Improvedextension, MySQLi offers prepared statements, bound

parameters, and SSL connections It even takes advantage ofPHP 5's new object-oriented support to provide an OO interface

supports transactions, subqueries, triggers, and many otheradvanced database features

Like MySQLi, SQLite also comes with dual procedural and OOinterfaces

1.2.3 XML

XML is a key part of web development, so PHP 5 offers a fullselection of new XML tools A major goal of XML in PHP 5 is

interoperability among each of the different XML extensions,making them a unified unit instead of individual agents

The new Document Object Model (DOM) extension is leaps andbounds better than PHP 4's experimental version It also usesnew PHP 5 features to comply with the DOM specification,

fulfilling the goal of DOM as a language-neutral API for XML

There's also a new Extensible Stylesheet Language

Transformations (XSLT) extension that operates on XML

documents and DOM objects You can transform DOM objectsusing XSLT and receive translated documents from XSLT Youcan even pass XML nodes back and forth between XSLT and PHPfrom within a stylesheet

Perhaps the most innovative part of PHP 5 is the SimpleXMLextension This lightweight interface to XML lets you easily

iterate through XML documents without the overhead of DOM orthe oddness of XSLT It's perfect for documents where you knowthe specification and want to quickly extract data

Chapter 5 covers all these topics, plus the original Simple APIfor XML (SAX) extension and an XPath extension, used for

1.2.6 Streams, Filters, and Wrappers

writing data using protocol-specific objects known as wrappers.Streams also let you modify the data flowing through them byattaching filters

First introduced in PHP 4.3, streams are an underutilized part ofPHP PHP 5 expands upon the existing streams infrastructure toallow more extensive wrappers, and to let you create filters

directly in PHP instead of in C

Chapter 8 demonstrates how to create a shared memory

wrapper and two streams, one for encoding HTML entities andanother for decoding them

1.2.7 Other Extensions

Chapter 9 covers three new pieces of PHP 5: SOAP, Tidy, andthe Reflection classes

SOAP is a key component of the fast-growing web services field.This extension lets developers create SOAP clients with or

without a Web Services Description Language (WSDL) file, andalso implement SOAP servers in PHP

The Tidy extension makes it easy to ensure that your output isvalid HTML and XHTML Its smart parser brings even the mostunruly of files into compliance with the latest W3C

specifications

Nothing less than complete code introspection is the goal of theReflection classes This set of classes lets you examine classes,methods, parameters, and more, to discover object attributes

It is now simple and easy to create PHP class browsers,

debuggers, and other tools that rely on gathering details aboutobjects and functions

This address book lets you add contact information and searchstored records using both a web and command-line interface.The output is completely separated from application logic, andthe program uses a simple series of template classes to controlits formatting

in many ways, it's easiest to be tripped up by minor changes.You know you're on new ground with the mysqli extension, but,unless you read Appendix B, you probably would not know thatyou can now pass optional parameters by reference, or thatstrrpos( ) behaves slightly differently than before, or eventhat the command-line version of PHP has the ability to execute

code on every line of input.

You can download PHP 5 from

http://www.php.net/downloads.php The installation process isidentical to PHP 4; however, PHP 5 does have some new

configuration options See Table C-1 in Appendix C for a

complete list

During the transition from PHP 4 to PHP 5, it's common to want

to run both versions of PHP simultaneously This lets you easilytest code under PHP 5 without switching completely away fromPHP 4 It also allows you to slowly migrate scripts from PHP 4 toPHP 5, as you can control which version of PHP parses specificsets of pages

One option is to run two separate web servers, either on

different machines or on different ports on the same machine.The primary advantage of using two web servers is that you canrun both PHP 4 and PHP 5 as a module The disadvantages arethat you either need multiple computers at your disposal or

need to be familiar with installing Apache (or your particularweb server of choice) It's also a lot of work for a temporarysituation

Another solution is to continue using your existing web serverand install one version of PHP as a module and another as aCGI This gets you up and running with both versions with

minimal fuss; however, the CGI version of PHP lacks certainfeatures included in the Apache module

Appendix C provides detailed instructions for setting up PHP 4and PHP 5 under Apache on both Unix and Windows It showshow to configure Apache to switch between the versions both

on a directory-by-directory basis and by setting up a virtual

server on another port

This chapter introduces object-oriented programming (OOP)and explains all the object-oriented (OO) features in PHP 5 Thechapter assumes no prior knowledge of OOP, so if this is yourfirst time learning it, that's okay

chapter shows you how and why you should modify your

existing code to take full advantage of PHP 5

Early versions of PHP were strictly procedural: you could definefunctions, but not objects PHP 3 introduced an extremely

rudimentary form of objects, written as a late-night hack Back

in 1997, nobody expected the explosion in the number of PHPprogrammers, nor that people would write large-scale programs

in PHP Therefore, these limitations weren't considered a

problem

Over the years, PHP gained additional object-oriented features;however, the development team never redesigned the core OOcode to gracefully handle objects and classes As a result,

although PHP 4 improved overall performance, writing complex

OO programs with it is still difficult, if not nearly impossible

PHP 5 fixes these problems by using Zend Engine 2 The firstversion of the Zend Engine was written for PHP 4 to handle

PHP's core functionality, such as what type of objects you canuse, and to define the language's syntax

If you don't have experience with object-oriented programmingoutside of PHP, then you're in for a bit of a surprise While some

of the new features allow you to do things more easily, manyfeatures don't let you do anything new at all In many ways,

they restrict what you can do.

Even though it seems counterintuitive, these limitations actuallyhelp you quickly write safe code because they promote codereuse and data encapsulation These key OO programming

concepts are explained throughout the chapter

accesses the table whenever it needs to fetch a person's emailaddress:

outside access This prevents people from relying on code thatmay change and forces them to use your functions to reach the

data Functions of this type are known as accessors, because

they allow access to otherwise protected information Whenredesigning code, if you update the accessors to work as

of data

Convert a class into an object by using the new keyword:

$rasmus = new Person;

This command causes PHP to look for a class labeled as Person,create a new copy, and assign it to $rasmus This process is

known as instantiating an object or creating a new instance of a

class

For now, don't worry about the actual syntax for defining

Person Also, it's not necessary to know how Person storesdata This information is encapsulated away, and you're forced

to invoke the setName( ) function on that specific instance ofthe class

author agrees that as long as a person uses accessor methods,such as setName( ) and getName( ), they'll always work, even

if the author redesigns the class

The full details on class creation come later, but here's a firstlook at the elements of a simple class For example, the Personclass can look like this: