Book Image

The PEAR Installer Manifesto

By : Gregory Beaver
Book Image

The PEAR Installer Manifesto

By: Gregory Beaver

Overview of this book

PEAR stands for PHP Extension and Application Repository, and its primary purpose is to support code re-use. PEAR provides both an advanced installer and a code repository at http://pear.php.net. PEAR code is organized into discrete re-usable components called packages. A package consists of a group of files and a descriptor file called package.xml that contains metadata about the package's contents, such as the package version, any special dependencies, and textual information such as the package description and authors. The software that transforms a package from an inert grouping of files into a dynamic software package is called the PEAR Installer and is itself a PEAR package. In other words, the PEAR Installer can be used to upgrade itself. It truly is a very powerful application. In short, the PEAR Installer is one of the most effective tools for managing a high-quality software library, high-quality applications, or high-quality websites. This book will show you a new way of organizing your PHP development, by leveraging the full power of the PEAR Installer. In a sense, the PEAR Installer is a step above a software design pattern, a meta-development pattern that can be used to systematically organize all of your PHP development. You will learn how to organize your code into packages using the package.xml format. You will learn about the revolutionary new PEAR Channel concept, and how to safely and reliably depend on external PHP libraries from sources such as pear.php.net and other PEAR channels. You will learn about the PEAR_PackageFileManager package, and how to customize individual installations of your PHP code through file roles, file tasks, and post-installation scripts. In addition, you will learn how to use the power of PEAR to manage your web projects with the PEAR installer to bring the power of versioning and rollbacks to your live website. The synergy of the PEAR Installer and a revision control system like CVS or Subversion is also explored in depth. Next, you will learn how to set up your own PEAR Channel for distributing PHP applications, both open-source and proprietary closed-source PHP applications that can be secured using technology already built into the PEAR Installer. Finally, you will learn how to embed the PEAR Installer inside your own web application in order to manage plug-ins from a remote server. The book covers in detail designing a custom plug-in system for a fictitious blog application. The plug-in system is used to manage templates, and the PEAR Installer is used to manage the details of querying the remote server for templates, handling dependencies between versioning, and doing the actual installation process as well.
Table of Contents (11 chapters)
The PEAR Installer Manifesto
Credits
About the Author
About the Reviewers
Preface

Preface

Chances are, you've seen the acronym PEAR at some point in your use of PHP, whether it was in passing or when installing and using a package from pear.php.net. If you've investigated, you've probably heard of popular software provided by PEAR, such as the DB database abstraction package, or the HTML_QuickForm package. What you may not realize is that PEAR is much more than just a collection of packages that you can use. PEAR also contains the most versatile installation program for PHP, the PEAR installer.

With the PEAR installer, you can do much more than just install packages from pear.php.net. You can install packages from other PEAR channels, distribute your own software projects using your own PEAR channel, and even maintain a complex web project, all using the PEAR installer. Surprised? Well read on, as this book reveals the intimate secrets of the PEAR installer and how it will revolutionize your everyday development with the PHP programming language!

What This Book Covers

Chapter 1 introduces you to the PEAR installer. We begin with a look at the traditional unzip-and-go method of distributing PHP software and compare its advantages and disadvantages to the PEAR installer's package-based method of distributing PHP software. You will see the innovation of PEAR channels, take a peek inside how the PEAR installer installs files from packages, and learn how it knows where to install them. Finally, you will see the many ways to acquire the PEAR installer and even how to install PEAR remotely onto a web host that does not provide shell access.

Chapter 2 is a must-read for all PHP developers, as it explains the basic workings of package.xml, the heart of the PEAR installer. package.xml is used to control almost everything the PEAR installer can do. You will learn about the importance of versioning in controlling the quality of packages installed, the importance of dependencies, and how the PEAR installer manages this important link between libraries and applications. You will also learn how package.xml organizes package metadata such as the package name, authors, release notes, and changelog, and has critical installation data such as files, dependencies, and versioning organized.

Chapter 3 goes further in depth for developers who want to take advantage of the full application-support features introduced in package.xml version 2.0.

Chapter 4 takes a break from looking at the details of the PEAR installer, and dives into using the PEAR installer to develop and to maintain a complicated and rapidly evolving website.

Chapter 5 covers PEAR channels. Channels are designed to make it easy to install packages from any location, but difficult to compromise your system in the process, following a basic security principle: always design things so that the easiest way to do them is the most secure.

Channels open up pear.php.net's monopoly over the PEAR installer to the entire Internet. Custom-built packages distributed through your channel can even be sold and made available to specific users while co-existing peacefully with publicly available open-source packages.

Chapter 6 teaches you how to embed the PEAR installer to create a plug-in manager. The chapter creates a fake blog application that provides the ability to seamlessly query a remote PEAR channel server designed to distribute templates. Using the internal classes of the PEAR installer, our blog web application intelligently installs and upgrades templates with all of the sophistication expected from the PEAR installer.

Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

There are three styles for code. Code words in text are shown as follows: "Next, you need to create a configuration file for the remote machine using the config-create command."

A block of code will be set as follows:

<file name="blah.php" role="php">
<tasks:replace from="@DATABASE-URL@" to="database_url"
type="pear-config" />
</file>

When we wish to draw your attention to a particular part of a code block, the relevant lines or items will be made bold:

if (is_object($infoplugin)) {
$bag = new serendipity_property_bag;
$infoplugin->introspect($bag);
if ($bag->get('version') == $data['version']) {
$installable = false;
} elseif (version_compare($bag->get('version'),
$data['version'], '<')) {
$data['upgradable'] = true;

$data['upgrade_version'] = $data['version'];
$data['version'] = $bag->get('version');

Any command-line input and output is written as follows:

$ pear c pear.ini remote-install o DB_DataObject

New terms and important words are introduced in a bold-type font. Words that you see on the screen, in menus or dialog boxes for example, appear in our text like this: "clicking the Next button moves you to the next screen".

Note

Warnings or important notes appear in a box like this.

Note

Tips and tricks appear like this.

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