THIRD EDITION

Programming PHP

Kevin Tatroe, Peter MacIntyre, and Rasmus Lerdorf

Beijing • Cambridge • Farnham • Kưln • Sebastopol • Tokyo


Programming PHP, Third Edition
by Kevin Tatroe, Peter MacIntyre, and Rasmus Lerdorf
Copyright © 2013 Kevin Tatroe, Peter MacIntyre. All rights reserved.
Printed in the United States of America.
Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472.
O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions
are also available for most titles (). For more information, contact our
corporate/institutional sales department: 800-998-9938 or

Editors: Meghan Blanchette and Rachel
Roumeliotis

Production Editor: Rachel Steely
Copyeditor: Kiel Van Horn
Proofreader: Emily Quill
February 2013:

Indexer: Angela Howard
Cover Designer: Karen Montgomery
Interior Designer: David Futato

Illustrators: Robert Romano and Rebecca Demarest

Third Edition.

Revision History for the Third Edition:
2013-02-05
First release
See for release details.

Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of
O’Reilly Media, Inc. Programming PHP, the image of a cuckoo, and related trade dress are trademarks
of O’Reilly Media, Inc.
Many of the designations used by manufacturers and sellers to distinguish their products are claimed as
trademarks. Where those designations appear in this book, and O’Reilly Media, Inc., was aware of a
trademark claim, the designations have been printed in caps or initial caps.
While every precaution has been taken in the preparation of this book, the publisher and authors assume
no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.

ISBN: 978-1-449-39277-2
[LSI]
1360094505


I would like to dedicate my portions of this book
to my wonderful wife, Dawn Etta Riley. I love you
Dawn!
—Peter MacIntyre




Table of Contents

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
1. Introduction to PHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
What Does PHP Do?
A Brief History of PHP
The Evolution of PHP
The Widespread Use of PHP
Installing PHP
A Walk Through PHP
Configuration Page
Forms
Databases
Graphics

1
2
2
6
7
7
8
9
10
13

2. Language Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Lexical Structure
Case Sensitivity

Statements and Semicolons
Whitespace and Line Breaks
Comments
Literals
Identifiers
Keywords
Data Types
Integers
Floating-Point Numbers
Strings
Booleans
Arrays

15
15
15
16
17
20
20
21
22
22
23
24
25
26

v



Objects
Resources
Callbacks
NULL
Variables
Variable Variables
Variable References
Variable Scope
Garbage Collection
Expressions and Operators
Number of Operands
Operator Precedence
Operator Associativity
Implicit Casting
Arithmetic Operators
String Concatenation Operator
Auto-increment and Auto-decrement Operators
Comparison Operators
Bitwise Operators
Logical Operators
Casting Operators
Assignment Operators
Miscellaneous Operators
Flow-Control Statements
if
switch
while
for
foreach

try...catch
declare
exit and return
goto
Including Code
Embedding PHP in Web Pages
Standard (XML) Style
SGML Style
ASP Style
Script Style
Echoing Content Directly

27
28
29
29
29
30
30
31
33
34
36
36
37
37
38
38
39
40

41
43
43
45
46
47
47
49
51
53
54
55
55
56
56
57
58
59
60
61
61
61

3. Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Calling a Function

vi | Table of Contents

63



Defining a Function
Variable Scope
Global Variables
Static Variables
Function Parameters
Passing Parameters by Value
Passing Parameters by Reference
Default Parameters
Variable Parameters
Missing Parameters
Type Hinting
Return Values
Variable Functions
Anonymous Functions

64
66
67
68
68
69
69
70
70
71
72
72
73
74


4. Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Quoting String Constants
Variable Interpolation
Single-Quoted Strings
Double-Quoted Strings
Here Documents
Printing Strings
echo
print()
printf()
print_r() and var_dump()
Accessing Individual Characters
Cleaning Strings
Removing Whitespace
Changing Case
Encoding and Escaping
HTML
URLs
SQL
C-String Encoding
Comparing Strings
Exact Comparisons
Approximate Equality
Manipulating and Searching Strings
Substrings
Miscellaneous String Functions
Decomposing a String
String-Searching Functions


77
77
78
78
79
80
81
81
81
83
85
85
85
86
86
87
89
90
91
92
92
93
94
95
96
97
98

Table of Contents | vii



Regular Expressions
The Basics
Character Classes
Alternatives
Repeating Sequences
Subpatterns
Delimiters
Match Behavior
Character Classes
Anchors
Quantifiers and Greed
Noncapturing Groups
Backreferences
Trailing Options
Inline Options
Lookahead and Lookbehind
Cut
Conditional Expressions
Functions
Differences from Perl Regular Expressions

100
101
102
103
103
104
104
105

105
106
107
108
108
108
109
110
111
112
112
117

5. Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Indexed Versus Associative Arrays
Identifying Elements of an Array
Storing Data in Arrays
Adding Values to the End of an Array
Assigning a Range of Values
Getting the Size of an Array
Padding an Array
Multidimensional Arrays
Extracting Multiple Values
Slicing an Array
Splitting an Array into Chunks
Keys and Values
Checking Whether an Element Exists
Removing and Inserting Elements in an Array
Converting Between Arrays and Variables
Creating Variables from an Array

Creating an Array from Variables
Traversing Arrays
The foreach Construct
The Iterator Functions
Using a for Loop

viii | Table of Contents

119
120
120
122
122
122
122
123
123
124
125
125
126
126
128
128
128
129
129
130
131



Calling a Function for Each Array Element
Reducing an Array
Searching for Values
Sorting
Sorting One Array at a Time
Natural-Order Sorting
Sorting Multiple Arrays at Once
Reversing Arrays
Randomizing Order
Acting on Entire Arrays
Calculating the Sum of an Array
Merging Two Arrays
Calculating the Difference Between Two Arrays
Filtering Elements from an Array
Using Arrays
Sets
Stacks
Iterator Interface

131
132
133
134
135
137
137
138
139
139

139
140
140
141
141
141
142
143

6. Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Terminology
Creating an Object
Accessing Properties and Methods
Declaring a Class
Declaring Methods
Declaring Properties
Declaring Constants
Inheritance
Interfaces
Traits
Abstract Methods
Constructors
Destructors
Introspection
Examining Classes
Examining an Object
Sample Introspection Program
Serialization

148

148
149
150
151
153
155
155
156
157
160
161
162
163
163
164
165
169

7. Web Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
HTTP Basics
Variables
Server Information

173
174
175
Table of Contents | ix


Processing Forms

Methods
Parameters
Self-Processing Pages
Sticky Forms
Multivalued Parameters
Sticky Multivalued Parameters
File Uploads
Form Validation
Setting Response Headers
Different Content Types
Redirections
Expiration
Authentication
Maintaining State
Cookies
Sessions
Combining Cookies and Sessions
SSL

177
177
178
180
182
182
185
186
187
189
190

190
191
191
192
193
197
199
200

8. Databases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
Using PHP to Access a Database
Relational Databases and SQL
PHP Data Objects
MySQLi Object Interface
Retrieving Data for Display
SQLite
Direct File-Level Manipulation
MongoDB
Retrieving Data
Inserting More Complex Data

203
204
205
208
209
211
214
222
224

226

9. Graphics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Embedding an Image in a Page
Basic Graphics Concepts
Creating and Drawing Images
The Structure of a Graphics Program
Changing the Output Format
Testing for Supported Image Formats
Reading an Existing File
Basic Drawing Functions
Images with Text
Fonts
x | Table of Contents

229
230
231
232
233
233
234
234
236
236


TrueType Fonts
Dynamically Generated Buttons
Caching the Dynamically Generated Buttons

A Faster Cache
Scaling Images
Color Handling
Using the Alpha Channel
Identifying Colors
True Color Indexes
Text Representation of an Image

237
239
240
241
243
244
245
246
247
248

10. PDF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
PDF Extensions
Documents and Pages
A Simple Example
Initializing the Document
Outputting Basic Text Cells
Text
Coordinates
Text Attributes
Page Headers, Footers, and Class Extension
Images and Links

Tables and Data

251
251
252
252
253
253
253
255
258
260
263

11. XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
Lightning Guide to XML
Generating XML
Parsing XML
Element Handlers
Character Data Handler
Processing Instructions
Entity Handlers
Default Handler
Options
Using the Parser
Errors
Methods as Handlers
Sample Parsing Application
Parsing XML with DOM
Parsing XML with SimpleXML

Transforming XML with XSLT

267
269
270
271
272
272
273
275
275
276
278
278
279
283
284
285

Table of Contents | xi


12. Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
Filter Input
Cross-Site Scripting
SQL Injection
Escape Output
Filenames
Session Fixation
File Uploads

Distrust Browser-Supplied Filenames
Beware of Filling Your Filesystem
Surviving register_globals
File Access
Restrict Filesystem Access to a Specific Directory
Get It Right the First Time
Don’t Use Files
Session Files
Concealing PHP Libraries
PHP Code
Shell Commands
More Information
Security Recap

289
292
292
294
298
299
300
300
301
301
301
302
302
303
303
304

304
305
306
306

13. Application Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
Code Libraries
Templating Systems
Handling Output
Output Buffering
Compressing Output
Error Handling
Error Reporting
Error Suppression
Triggering Errors
Defining Error Handlers
Performance Tuning
Benchmarking
Profiling
Optimizing Execution Time
Optimizing Memory Requirements
Reverse Proxies and Replication

309
310
313
313
315
315
316

317
317
318
321
322
324
325
325
326

14. PHP on Disparate Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Writing Portable Code for Windows and Unix
Determining the Platform
xii | Table of Contents

329
330


Handling Paths Across Platforms
The Server Environment
Sending Mail
End-of-Line Handling
End-of-File Handling
External Commands
Common Platform-Specific Extensions
Interfacing with COM
Background
PHP Functions
Determining the API


330
330
331
331
332
332
332
333
333
335
335

15. Web Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
REST Clients
Responses
Retrieving Resources
Updating Resources
Creating Resources
Deleting Resources
XML-RPC
Servers
Clients

337
339
341
342
343
344

344
344
346

16. Debugging PHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
The Development Environment
The Staging Environment
The Production Environment
php.ini Settings
Manual Debugging
Error Log
IDE Debugging
Additional Debugging Techniques

349
350
351
351
353
355
355
357

17. Dates and Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
Appendix: Function Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

Table of Contents | xiii




Foreword

When the authors first asked me if I’d be interested in writing a foreword for the third
edition of this book, I eagerly said yes—what an honor. I went back and read the
foreword from the previous edition, and I got overwhelmed. I started to question why
they would ask me to write this in the first place. I am not an author; I have no amazing
story. I’m just a regular guy who knows and loves PHP! You probably already know
how widespread PHP is in applications like Facebook, Wikipedia, Drupal, and Wordpress. What could I add?
All I can say is that I was just like you not too long ago. I was reading this book to try
and understand PHP programming for the first time. I got into it so much that I joined
Boston PHP (the largest PHP user group in North America) and have been serving as
lead organizer for the past four years. I have met all kinds of amazing PHP developers,
and the majority of them are self-taught. Chances are that you, like most PHP people
I know (including myself), came into the language quite by accident. You want to use
it to build something new.
Our user group once held an event where we invited everyone in the community to
come and demonstrate a cool new way to use PHP. A realtor showed us how to create
a successful business with an online virtual reality application that lets you explore real
estate in your area with beautiful views of properties. An educational toy designer
showed us his clever website to market his unique educational games. A musician used
PHP to create music notation learning tools for a well-known music college. Yet another
person demoed an application he built to assist cancer research at a nearby medical
institution.
As you can see, PHP is accessible and you can do almost anything with it. It’s being
used by people with different backgrounds, skill sets, and goals. You don’t need a
degree in computer science to create something important and relevant in this day and
age. You need books like this one, communities to help you along, a bit of dedication,
and some elbow grease, and you’re on your way to creating a brand-new tool.


xv


Learning PHP is easy and fun. The authors have done a great job of covering basic
information to get you started and then taking you right through to some of the more
advanced topics, such as object-oriented programming. So dig in, and practice what
you read in this book. You should also look for PHP communities, or user groups, in
your area to help you along and to get “plugged in.” There are also many PHP conferences going on in other parts of the world, as this list shows. Boston PHP, along with
two other user groups, hosts a PHP conference each year in August. Come and meet
some excellent folks (both Peter MacIntyre, one of the co-authors, and I will be there)
and get to know them; you’ll be a better PHPer because of it.
—Michael P. Bourque
VP, PTC
Organizer for Boston PHP User Group
Organizer for Northeast PHP Conference
Organizer for The Reverse Startup

xvi | Foreword


Preface

Now more than ever, the Web is a major vehicle for corporate and personal communications. Websites carry satellite images of Earth in its entirety, search for life in outer
space, and house personal photo albums, business shopping carts, and product lists.
Many of those websites are driven by PHP, an open source scripting language primarily
designed for generating HTML content.
Since its inception in 1994, PHP has swept the Web and continues its phenomenal
growth with recent endorsements by IBM and Oracle (to name a few). The millions of
websites powered by PHP are testament to its popularity and ease of use. Everyday
people can learn PHP and build powerful dynamic websites with it. Marc Andreessen,

partner in Andreessen Horowitz and founder of Netscape Communications, recently
described PHP as having replaced Java as the ideal programming language for the Web.
The core PHP language (version 5+) features powerful string- and array-handling facilities, as well as greatly improved support for object-oriented programming. With the
use of standard and optional extension modules, a PHP application can interact with
a database such as MySQL or Oracle, draw graphs, create PDF files, and parse XML
files. You can write your own PHP extension modules in C—for example, to provide
a PHP interface to the functions in an existing code library. You can even run PHP on
Windows, which lets you control other Windows applications, such as Word and Excel
with COM, or interact with databases using ODBC.
This book is a guide to the PHP language. When you finish it, you will know how the
PHP language works, how to use the many powerful extensions that come standard
with PHP, and how to design and build your own PHP web applications.

Audience
PHP is a melting pot of cultures. Web designers appreciate its accessibility and convenience, while programmers appreciate its flexibility, power, diversity, and speed. Both
cultures need a clear and accurate reference to the language. If you are a programmer,
then this book is for you. We show the big picture of the PHP language, and then discuss
the details without wasting your time. The many examples clarify the explanations,

xvii


and the practical programming advice and many style tips will help you become not
just a PHP programmer, but a good PHP programmer.
If you’re a web designer, you will appreciate the clear and useful guides to specific
technologies, such as XML, sessions, PDF generation, and graphics. And you’ll be able
to quickly get the information you need from the language chapters, which explain
basic programming concepts in simple terms.
This book has been fully revised to cover the latest features of PHP version 5.


Assumptions This Book Makes
This book assumes you have a working knowledge of HTML. If you don’t know HTML,
you should gain some experience with simple web pages before you try to tackle PHP.
For more information on HTML, we recommend HTML & XHTML: The Definitive
Guide by Chuck Musciano and Bill Kennedy (O’Reilly).

Contents of This Book
We’ve arranged the material in this book so that you can either read it from start to
finish or jump around to hit just the topics that interest you. The book is divided into
17 chapters and 1 appendix, as follows:
Chapter 1, Introduction to PHP
Talks about the history of PHP and gives a lightning-fast overview of what is possible with PHP programs.
Chapter 2, Language Basics
Is a concise guide to PHP program elements such as identifiers, data types, operators, and flow-control statements.
Chapter 3, Functions
Discusses user-defined functions, including scope, variable-length parameter lists,
and variable and anonymous functions.
Chapter 4, Strings
Covers the functions you’ll use when building, dissecting, searching, and modifying strings in your PHP code.
Chapter 5, Arrays
Details the notation and functions for constructing, processing, and sorting arrays
in your PHP code.
Chapter 6, Objects
Covers PHP’s updated object-oriented features. In this chapter, you’ll learn about
classes, objects, inheritance, and introspection.

xviii | Preface


Chapter 7, Web Techniques

Discusses web basics such as form parameters and validation, cookies, and sessions.
Chapter 8, Databases
Discusses PHP’s modules and functions for working with databases, using the
PEAR database library and the MySQL database as examples. Also, the new SQLite
database engine and the new PDO database interface are covered.
Chapter 9, Graphics
Demonstrates how to create and modify image files in a variety of formats from
within PHP.
Chapter 10, PDF
Explains how to create dynamic PDF files from a PHP application.
Chapter 11, XML
Introduces PHP’s updated extensions for generating and parsing XML data.
Chapter 12, Security
Provides valuable advice and guidance for programmers creating secure scripts.
You’ll learn best practices programming techniques here that will help you avoid
mistakes that can lead to disaster.
Chapter 13, Application Techniques
Talks about advanced techniques most PHP programmers eventually want to use,
including error handling and performance tuning.
Chapter 14, PHP on Disparate Platforms
Discusses the tricks and traps of the Windows port of PHP. It also discusses some
of the features unique to Windows such as COM.
Chapter 15, Web Services
Provides techniques for creating a modern web services API via PHP, and for connecting with web services APIs on other systems.
Chapter 16, Debugging PHP
Discusses techniques for debugging PHP code and for writing debuggable PHP
code.
Chapter 17, Dates and Times
Talks about PHP’s built-in classes for dealing with dates and times.
Appendix

A handy quick reference to all core functions in PHP.

Conventions Used in This Book
The following typographical conventions are used in this book:
Italic
Indicates new terms, URLs, email addresses, filenames, and file extensions.
Preface | xix


Constant width

Used for program listings, as well as within paragraphs to refer to program elements
such as variable or function names, databases, data types, environment variables,
statements, and keywords.
Constant width bold

Shows commands or other text that should be typed literally by the user.
Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.
This icon signifies a tip, suggestion, or general note.

This icon indicates a warning or caution.

Using Code Examples
This book is here to help you get your job done. In general, if this book includes code
examples, you may use the code in your programs and documentation. You do not
need to contact us for permission unless you’re reproducing a significant portion of the
code. For example, writing a program that uses several chunks of code from 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 book and
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 attribution usually includes the title,
author, publisher, and ISBN. For example: “Programming PHP by Kevin Tatroe, Peter
MacIntyre, and Rasmus Lerdorf (O’Reilly). Copyright 2013 Kevin Tatroe and Peter
MacIntyre, 978-1-449-39277-2.”
If you feel your use of code examples falls outside fair use or the permission given above,
feel free to contact us at

Safari® Books Online
Safari Books Online (www.safaribooksonline.com) is an on-demand digital
library that delivers expert content in both book and video form from the
world’s leading authors in technology and business.
xx | Preface


Technology professionals, software developers, web designers, and business and creative professionals use Safari Books Online as their primary resource for research,
problem solving, learning, and certification training.
Safari Books Online offers a range of product mixes and pricing programs for organizations, government agencies, and individuals. Subscribers have access to thousands
of books, training videos, and prepublication manuscripts in one fully searchable database from publishers like O’Reilly Media, Prentice Hall Professional, Addison-Wesley
Professional, Microsoft Press, Sams, Que, Peachpit Press, Focal Press, Cisco Press, John
Wiley & Sons, Syngress, Morgan Kaufmann, IBM Redbooks, Packt, Adobe Press, FT
Press, Apress, Manning, New Riders, McGraw-Hill, Jones & Bartlett, Course Technology, and dozens more. For more information about Safari Books Online, please visit
us online.

How to Contact Us
Please address comments and questions concerning this book to the publisher:
O’Reilly Media, Inc.

1005 Gravenstein Highway North
Sebastopol, CA 95472
800-998-9938 (in the United States or Canada)
707-829-0515 (international or local)
707-829-0104 (fax)
We have a web page for this book, where we list errata, examples, and any additional
information. You can access this page at />To comment or ask technical questions about this book, send email to

For more information about our books, courses, conferences, and news, see our website
at .
Find us on Facebook: />Follow us on Twitter: />Watch us on YouTube: />
Acknowledgments
Kevin Tatroe
Thanks to every individual who ever committed code to PHP or who wrote a line of
code in PHP—you all made PHP what it is today.

Preface | xxi


To my parents, who once purchased a small LEGO set for a long and frightening plane
trip, beginning an obsession with creativity and organization that continues to relax
and inspire.
Finally, a heaping third spoonful of gratitude to Jennifer and Hadden, who continue
to inspire and encourage me even as I pound out words and code every day.

Peter MacIntyre
I would first like to praise the Lord of Hosts who gives me the strength to face each
day. He created electricity through which I make my livelihood; thanks and praise to
Him for this totally unique and fascinating portion of His creation.
To Kevin, who is once again my main coauthor on this edition, thanks for the effort

and desire to stick with this project to the end.
To the technical editors who sifted through our code examples and tested them to make
sure we were accurate—Simon, Jock, and Chris—thanks!
And finally to all those at O’Reilly who so often go unmentioned—I don’t know all
your names, but I know what you have to do to make a book like this finally make it
to the bookshelves. The editing, graphics work, layout, planning, marketing, and so
on all has to be done, and I appreciate your work toward this end.

xxii | Preface


CHAPTER 1

Introduction to PHP

PHP is a simple yet powerful language designed for creating HTML content. This
chapter covers essential background on the PHP language. It describes the nature and
history of PHP, which platforms it runs on, and how to configure it. This chapter ends
by showing you PHP in action, with a quick walkthrough of several PHP programs that
illustrate common tasks, such as processing form data, interacting with a database, and
creating graphics.

What Does PHP Do?
PHP can be used in three primary ways:
Server-side scripting
PHP was originally designed to create dynamic web content, and it is still best
suited for that task. To generate HTML, you need the PHP parser and a web server
through which to send the coded documents. PHP has also become popular for
generating XML documents, graphics, Flash animations, PDF files, and so much
more.

Command-line scripting
PHP can run scripts from the command line, much like Perl, awk, or the Unix shell.
You might use the command-line scripts for system administration tasks, such as
backup and log parsing; even some CRON job type scripts can be done this way
(nonvisual PHP tasks).
Client-side GUI applications
Using PHP-GTK, you can write full-blown, cross-platform GUI applications in
PHP.
In this book, however, we concentrate on the first item: using PHP to develop dynamic
web content.

1