With the growing interest in Drupal as a platform for developing websites, the number of books devoted to this CMS has increased from a handful to now several dozen. Consequently, intermediate and advanced Drupal programmers may wonder which one of those books would be their best choice as a single resource for learning how to create custom Drupal modules and themes. Ever since its first edition in April 2007, the Pro Drupal Development series from Apress is more frequently cited as the best candidate than any other.
In its third edition, Pro Drupal 7 Development is now helmed by Todd Tomlinson and John K. VanDyke, and again features a forward by Dries Buytaert, the founder and project lead of Drupal. This edition was published on 29 December 2010 under the ISBN 978-1430228387. The publisher offers a fairly sparse Web page for the book, containing a brief description, the source code used in the book, a page for errata (several reported), links to purchase both the print and electronic versions (oddly, with no bundle discount), and a section for author information, which currently has no entries. At 720 pages, it is the longest Drupal book on the market, as of this writing (and should remain so until the scheduled release of Wiley's Drupal 7 Bible). Yet Pro Drupal 7 Development is not terribly thick, probably because its paper appears to be thinner than that typically used for programming books. Although this allows the text on the other side of each page to show through slightly (and no doubt unintentionally), it generally does not pose a problem, but would have if a paper any thinner had been chosen.
The book's material is organized into 25 chapters and two appendices, covering numerous topics: Drupal infrastructure, including requisite Web technologies; module development basics; hooks, actions, and triggers; the menu, database, user, node, field, and theme systems; blocks; the form API; the filter system; searching and indexing content; file management; taxonomy and vocabularies; caching; sessions; jQuery; localization, internationalization, and content translation; XML-RPC; how to develop secure code and other best practices; site optimization; installation profiles; testing; Drupal database reference; and other resources. Given the sizable number of chapters and topics explored in this book, it would be impractical to attempt to provide any sort of full synopsis in this review. Instead I will focus more attention on those topics that will be of greater importance to Drupal developers (a phrase used to distinguish them from any Drupal site builders who do not create their own modules or modify existing ones).
The subject matter presented first — how to structure module code and make use of Drupal's hook system, as well as actions and triggers — is essential reading for anyone new to these topics (but presumably could be skipped by any veteran programmer familiar with them from earlier versions of Drupal). Most readers should find that there is sufficient information provided to understand the concepts and/or the code being presented, but there are a few exceptions: For instance, on page 22, the narrative refers to only a single node, but the code in annotate_node_load() suggests multiple nodes are being processed. Also, readers following along by implementing the example code, will likely be frustrated that the action "Beep multiple times" is not displayed in their own "Trigger: After saving new content" list box (page 42). Fortunately, these are the exceptions, because the authors present the ideas at a measured pace, with sufficient groundwork so readers will not become lost.
An understanding of Drupal's powerful hook system, is a necessary foundation for learning the concepts that form the heart of this book — namely, the menu, database, user, node, field, theme, block, and form systems (often referred to as the Drupal APIs). The presentation of the ideas is done in a methodical fashion, with plenty of example code and screenshots. Readers who patiently work their way through the material — particularly if they try to get the code working in their own Drupal environments, and perhaps even experiment with variations — will likely find it a time-consuming process, yet they will be richly rewarded for their efforts. The only blemishes are the several places in the text where there is a mismatch between the narrative and the code, or between the code and a screenshot. Several examples should suffice: The menufun_hello() function on page 67 is missing code for the two @from variables. Page 76 refers to a mysterious "second parameter, $b". The $items code on page 77 is close to what is in Drupal 6's user.module, but is nothing like Drupal 7's. Remarkably, "%index" appears in a section head (page 79) but nowhere in the text. The pager display code (on page 96) is missing "$result = $query->execute();". A "module named dbtest" (page 111) doesn't seem to exist.
The topics covered next in the book generally go beyond the Drupal APIs, and are much more diverse. Readers will learn how to filter user input, as well as how to allow users to search a site's content, upload files, and characterize nodes using terms from taxonomy vocabularies. Incidentally, the chapter on caching would have been better positioned just before the chapter on optimizing Drupal's performance, since the two areas are so closely related. Yet both are invaluable for minimizing the page load times for any substantial Drupal-based site. The authors show how, within Drupal modules, to utilize jQuery and XML-RPC. The chapter devoted to localization and translation — a subject growing in importance as sites go multilingual — is quite thorough.
The last five chapters of the book address topics that can help anyone become a better Drupal developer: code and form input security, programming best practices, Drupal site optimization, installation profiles, and testing techniques. Even though the authors provide a full chapter on Drupal programming best practices, there are similar nuggets of wisdom sprinkled throughout the other chapters — evidence of the authors' deep experience writing Drupal code, and seeing the pitfalls. The book's two appendices consist of a Drupal database reference, which describes all of the tables and their columns, and a summary of Drupal resources aside from the book, including user groups. The book concludes with an index that is missing some key concepts (e.g., permissions and roles), and would have been able to include more entries if the publisher had not chosen to use an unnecessarily large font and line height.
Each chapter concludes with a brief summary, and all of these summaries provide no value and should be dropped from any future editions. For each one of the items labeled "Note" (scattered throughout the book), if it repeats information mentioned in the text (some just a couple sentences earlier), then it should be excised; otherwise, the information should be folded into the text. The book's narrative could be improved in other ways: There are a number of instances where the authors refer to particular lines of code in the example code, and it would have been most convenient for the reader had line numbers been used. Module names are often incorrectly presented in all lowercase (e.g., page 13). Occasionally some phrases or acronyms should have been explained (or not used), such as "HA companies" (page xxix). On the plus side, the material is occasionally livened up with some welcome humor, such as the devilish functionality of "Evil Bob's Forum BonusPak" (page 14) and some equally devilish deadly pets (page 282). At first, readers may chuckle at the phrase "Drupal's legendary snappiness" (page 499), but evidently the authors were not being facetious.
The example code sprinkled throughout the chapters is especially helpful to the reader, and there are only a few places where the code does not match the narrative, or the code is incorrect in some other way (aside from those instances mentioned above): The text on page 14 neglected "annotate.admin.inc"; and in the listing for annotate.info, the "configure" path should not include "content/". In the discussion on paged display (on page 96), "clicking on 5 would take the visitor to rows" 41 through 50, and not "51 through 60". The code on pages 147 and 149 erroneously refers to "punchline" and a joke node type in job_node_access(). On page 355, field_tags is identified as field_geographic_location. The contents of the files in the downloadable source code do not always match what is seen in the book, starting with annotate.info (page 14) and annotate_admin_settings_submit() (page 20). Even worse, the source code for Chapters 3-6, 12, 13, 15-17, 19-22, 24, and 25 is missing completely.
There are numerous other, more simple errata: "-sites" (page 8), "an[d] installing" (9), "/q=node/3" (10; missing the '?'), "modules /" (17), "[the module] removes" (19), "hooks key" (45; should read "triggers key"), "beep_multiple_.beep_.action()" (49), "end" (55; should read "beginning"), "to [the] module" (61), curly quotes in code (63, 67, 190, etc.), "%user_uid_only_optional" (77), "function_menufun_menu()" (79), "product" (98; should read "produce"), "lower-case" (111), "users signature" (117), "[the] time" (118), "themeing" (153), "seconary" (190), "to and an" (308), "php", "class. the", and "apis" (all on page 323), and "pave" (409). At that point, I stopped recording the errata. Most if not all of these errors should have been spotted in the book's technical review process, assuming they were not introduced after the reviews were done.
For computer programming books, information presented outside of the narrative — such as figures and example source code — can either greatly enhance the reader's experience, or undermine it. In Pro Drupal 7 Development, the diagrams and screenshots are relatively few in number, yet are used effectively, with only a few errors: The caption for Figure 3-8 appears to be incorrect, as is the URL in Figure 4-5. Figure 5-1 contains an erroneous "$database". Table 17-1 is missing a row for uid 0. The screenshots in Figures 19-1 and 19-2 are quite fuzzy and difficult to read.
A few comments on the book's physical design and production are called for: In the review copy that the publisher kindly sent me, the first text block signature consists of only the first two leaves. As a consequence, that signature had almost no glue holding it into the binding, and had already started to separate from the binding. The production team should have anticipated this sort of problem; but it may have been a choice driven by pending changes to the title and/or copyright pages.
Fortunately, none of the above flaws are significant compared to the wealth of information provided by this book. Pro Drupal 7 Development clearly demonstrates why, in the minds of countless Drupal developers, this series is the gold standard for learning the inner workings of Drupal, and how to utilize them for building custom modules.