Learning Joomla! 1.5 Extension Development

One of the most powerful and popular content management systems (CMSs) is Joomla, a superior derivative of Mambo. Out of the box, Joomla makes it relatively easy to build websites that allow collaborative editing of content, attractive styling via prebuilt templates, and many more features. A Joomla-based site can be further improved by adding custom modules, components, and other extensions to the CMS, without any modification to the core Joomla code. A resource that explains how to do this, is Learning Joomla! 1.5 Extension Development: Creating Modules, Components, and Plugins with PHP, by Joseph L. LeBlanc.

The book is put out by Packt Publishing, on 12 June 2007, under the ISBN 978-1847191304. The publisher maintains a page on their site dedicated to the book, where visitors can read summaries of the chapters and the overall book, order the e-book version (in PDF format) at a discount, download the book's sample source code, read and submit errata and feedback, and download a sample chapter, namely, "Chapter 1: Joomla! Extension Development: An Overview" (also in PDF format). Note that, as of this writing, the errata and feedback do not have their own links, but are located on the page accessible via the link "Code download", which should be clarified.

The book's title page bills it as "A practical tutorial for creating your first Joomla! 1.5 extensions with PHP", and that is exactly what the book is. Rather than organizing the information in a cookbook style — which is quite popular in programming books nowadays — this particular one uses a narrative approach, in which the author illustrates the concepts by stepping the reader through an example project. He begins with a clean install of Joomla, without any of the sample data, and shows how to "build extensions to create, find, promote, and cross-link restaurant reviews".

The nine chapters of the book are organized in a logical manner, and in the order that the typical developer would go about extending a Joomla-based site: overview; Joomla's component structure and registration; backend and front-end development; module development; using the model-view-controller design pattern (MVC); creating plugins; adding configurability for the extensions that you have created; packaging the extension elements for use by other Joomla developers.

In explaining the key concepts and procedures for building custom extensions to a Joomla site, the author takes a methodical approach, with a healthy balance between exposition, sample code, and illustrative figures. The chapters read quickly, and the code changes from one section to the next are helpfully bolded. The chapter summaries, as with most programming books, add no value, and could be beneficially dropped, thereby saving space.

The author states in the first chapter that there are three types of extensions within Joomla: components, modules, and plugins. This could be confusing to anyone who has read the articles that help introduce Joomla to the new developer, and are contained in the sample data found in Joomla version 1.5. Those articles include one titled "Extensions", which lists two additional extension types — templates and languages — not considered such by LeBlanc. However, that article does not make clear as to why templates and languages should even be considered extensions, which seems counterintuitive at first glance.

The presentation of all of the material in LeBlanc's book is not perfect, but it is certainly more than adequate. It is unfortunate that the book does not have a lay-flat binding, which tends to be more of a problem with slender volumes such as this one (176 pages), since much thicker books have more weight to keep both sides down on the table at the same time when the book is open. All of the screenshots have a bit too much pixelation, which makes the smallest text within the screenshots more difficult to read. However, none of that text is unreadable. The book's text outside of the screenshots is quite easy to read, with a generously-sized font and a logical layout of each page's material. Almost every page has two horizontal lines, one at the top, and one at the bottom; they serve no purpose, and could be eliminated to save ink and space, as could the brackets around every page number. The same is true for the much larger and thicker brackets used to delineate warnings, notes, tips, and tricks. There were a few other very minor flaws in the book. For instance, in the information about the reviewer, "MySQL" is misspelled. In the Table of Contents, the "Available Toolbar Buttons" line appears to be one font size too small, and thus inconsistent with the other subsection heads. All of these weaknesses are of little consequence and could be fixed in the next edition.

Even if a reader initially had no interest in developing their own extensions to Joomla, this book could easily spark their interest, given that the book shows just how powerful those extensions can be, as well as how doable they are, by any competent programmer familiar with PHP and MySQL. In fact, even if the reader were to later decide that they had no interest in creating any extensions, they could still benefit from the book's discussion of how components are structured within Joomla — a more clear explanation than anything I have seen in the official Joomla documentation. Joomla may be an excellent CMS, but the documentation quality does not come close to the value of Joomla itself. That is why there is such a great need for books such as this one.

Although Learning Joomla! 1.5 Extension Development: Creating Modules, Components, and Plugins with PHP has some weaknesses — as do most if not all technical books nowadays — for any developer interested in getting the most out of Joomla by building custom extensions, LeBlanc's contribution should prove especially informative and useful.