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Table of ContentsChapter 7: Custom Post Types167Chapter 8: Versioning Your Code with Subversion (SVN)191Chapter 9: Preparing Your Plugin for Distribution213Background: What's in a name?Understanding register post type()Customizing our post typeUsing shortcodesTesting our shortcodeCustomizing our pluginCreating a settings shortcut linkCleaning up when uninstallingSummaryWhy Subversion?Understanding the terminology and conceptsChecking out a local working copySVN folder structureCheckout, revisitedSetting up an SVN repositoryChecking out a local working copy of our repoAdding filesCommitting changes to the repositoryOvercoming errorsVerifying the new state of your repositoryAdding more files to your repositoryRemoving files from the repositoryUpdating your working copyTagging a versionReverting an entire projectReverting a single fileMoving filesExporting your working copyQuick referenceSummaryPublic enemy number one: PHP noticesPHP short tagsConflicting namesModifying loader.phpTesting WordPress versionTesting PHP versionTesting MySQL 206207208208209211213215215220222222

Table of ContentsTesting PHP modulesTesting WordPress installed pluginsCustom testsUnit testsWordPress limitationsHealth check pageStoring test results in the databaseDeath to clippy: Use sensible configurationsDouble check your interfaceDocumentationIdentify the purposeLearning to drive: Keeping it relevantPhrasebooks vs. dictionaries: Give examplesAnalogy: The three bearsAnalogy: PC load letterThe decalog of documentationSummaryChapter 10: Publishing Your PluginInternationalization and localizationProcessing each messageChoosing a textdomainBest practicesWorking with formattingMore advanced messagesPlural vs. singularMore complex messagesNotes to translatorsLanguage filesCreating a POT fileCreating translations: .po filesLoading a textdomainUpdating a translationFormat for the readme.txt fileSection – installationSection – Frequently Asked QuestionsSection – screenshotsNew addition – videosSection – summaryRequesting and using SVN accessPublicity and promotionSummary[ vi 245246248250251252253253253254254255257258

Table of ContentsAppendix A: Recommended Resources259Appendix B: WordPress API Reference263PHP referenceFunction referenceThe WordPress forumsWebDev StudiosViper007BondKovsheninSLTaylorXPlus3WP EngineerOther pluginsPHP functionsdirnamefile get contentspreg matchpreg replaceprint rsprintfstrtolowersubstrWordPress Functionseadd actionadd filteradd meta boxadd options pagecheck admin refereresc htmlget optionget post metaget the IDregister post typeremove meta boxscreen iconthe contentthe metaupdate post metawp count posts[ vii 268268268268269269269269269270270

Table of Contentswp diewp nonce fieldActionsadmin initadmin menudo meta boxesinitsave postwidgets initwp headFiltersthe 3[ viii ]www.it-ebooks.info

PrefaceBy picking up this book, there's a good chance that you fall into one of twocategories: an existing WordPress user / hobbyist programmer who is interested inbuilding your own plugins for the platform, or a seasoned developer who is new toWordPress and need to complete a project for a client.In either case, this book is designed to help you along the way. If you can code yourown plugins, you can make WordPress do just about anything. By learning how totap into the additional power and functionality that plugins provide, you can makeyour site easier to administer, add new features, or even alter the very nature of howWordPress works. Written with the WordPress version 3 in mind, this book willshow you how to build a variety of plugins that demonstrate the additional poweravailable to you as a plugin author.Throughout this book, our goal is to teach you all aspects of modern WordPressdevelopment. We will build a variety of WordPress plugins and follow their creationfrom the idea to the finishing touches. You will discover how to deconstruct anexisting plugin, use the WordPress API in typical scenarios, hook into the database,version your code with SVN, and deploy your new plugin to the world.We have plenty of work to do, so let's get started!What this book coversChapter 1, Preparing for WordPress Development, provides an overview of thedevelopment process and discusses a number of tools and practices recommendedfor a successful WordPress development environment.Chapter 2, Anatomy of a Plugin, breaks an existing plugin down into its componentparts to see what makes it work, and what makes it break.www.it-ebooks.info

PrefaceChapter 3, Social Bookmarking, walks through the development of an initial plugin,including how to tie into the WordPress API, how to trigger functions, and how toinclude external JavaScript files.Chapter 4, Ajax Search, covers the construction of a plugin that augments WordPress'built-in search capability. This chapter provides details on how to utilize Ajax andJQuery, as well as how to use the PHP library classes with static functions in ourplugins.Chapter 5, Content Rotator, explores the wonderful world of WordPress widgets. Inthis chapter we will show you how to build and manipulate a widget, as well as howto construct a personal preference page for your plugin.Chapter 6, Standardized Custom Content, begins the process of extending WordPress'usage as a content management system. We will cover how to alter and extendcustom fields and how to display custom content in your templates.Chapter 7, Custom Post Types, continues the discussion on extending WordPress asa CMS. We will also discuss working with shortcodes, and how to customize yourplugin by creating custom menus and administration panels in the Dashboard.Chapter 8, Versioning Your Code with Subversion (SVN), shows you how to maintainand manage your plugin code with a version control system.Chapter 9, Preparing Your Plugin for Distribution, takes the next logical step in makingsure your shiny new plugins are ready for the wider world. We will discuss how toavoid certain pitfalls by writing custom tests to check for failure points.Chapter 10, Publishing Your Plugin, covers the mechanics of officially making yourmasterpiece available to the public, including the topics of internationalization, usingthe WordPress SVN repository, and handling the ubiquitous readme.txt file.Appendix A, Recommended Resources, lists some of our favorite websites, books, andother resources for seeking additional knowledge or getting help with a specificproblem.Appendix B, WordPress API Reference, provides a compendium of functions, actions,and filters referenced in this book.What you need for this bookTo develop plugins for WordPress, all you really need is a text editor, a workinginstallation of WordPress, and your favorite (s)FTP program. Other tools, such as aMySQL editor, can make your life easier, but are optional.[2]www.it-ebooks.info

PrefaceWho this book is forThis book is for WordPress users who want to learn how to create their own pluginsand for developers who are new to the WordPress platform. Basic knowledge of PHPand HTML is expected, as well as a functional knowledge of how WordPress worksfrom a user standpoint.ConventionsIn this book, you will find a number of styles of text that distinguish betweendifferent kinds of information. Here are some examples of these styles, and anexplanation of their meaning.Code words in text are shown as follows: "We can include other contexts through theuse of the include directive."A block of code is set as follows: h3 class "widget-title" Built In WordPress Search Widget /h3 form role "search" method "get" id "searchform" action "http://localhost:8888/" div label class "screen-reader-text" for "s" Search for: /label input type "text" value "" name "s" id "s" / input type "submit" id "searchsubmit" value "Search" / /div When we wish to draw your attention to a particular part of a code block, therelevant lines or items are set in bold:/*Theme Name: Twenty Ten v2Theme URI: http://wordpress.org/Any command-line input or output is written as follows:svn checkout trunk/--username mygoogleidNew terms and important words are shown in bold. Words that you see on thescreen, in menus or dialog boxes for example, appear in the text like this: " Under theHello Dolly title, click on the Activate link.".[3]www.it-ebooks.info

PrefaceWarnings or important notes appear in a box like this.Tips and tricks appear like this.Reader feedbackFeedback from our readers is always welcome. Let us know what you think aboutthis book—what you liked or may have disliked. Reader feedback is important for usto develop titles that you really get the most out of.To send us general feedback, simply send an e-mail to feedback@packtpub.com,and mention the book title via the subject of your message.If there is a book that you need and would like to see us publish, please sendus a note in the SUGGEST A TITLE form on www.packtpub.com or e-mailsuggest@packtpub.com.If there is a topic that you have expertise in and you are interested in either writingor contributing to a book, see our author guide on www.packtpub.com/authors.Customer supportNow that you are the proud owner of a Packt book, we have a number of things tohelp you to get the most from your purchase.Downloading the example code for this bookYou can download the example code files for all Packt books you have purchasedfrom your account at http://www.PacktPub.com. If you purchased this bookelsewhere, you can visit http://www.PacktPub.com/support and register to havethe files e-mailed directly to you.[4]www.it-ebooks.info

PrefaceErrataAlthough we have taken every care to ensure the accuracy of our content, mistakesdo happen. If you find a mistake in one of our books—maybe a mistake in the text orthe code—we would be grateful if you would report this to us. By doing so, you cansave other readers from frustration and help us improve subsequent versions of thisbook. If you find any errata, please report them by visiting http://www.packtpub.com/support, selecting your book, clicking on the errata submission form link, andentering the details of your errata. Once your errata are verified, your submissionwill be accepted and the errata will be uploaded on our website, or added to any listof existing errata, under the Errata section of that title. Any existing errata can beviewed by selecting your title from http://www.packtpub.com/support.PiracyPiracy of copyright material on the Internet is an ongoing problem across all media.At Packt, we take the protection of our copyright and licenses very seriously. If youcome across any illegal copies of our works, in any form, on the Internet, pleaseprovide us with the location address or website name immediately so that we canpursue a remedy.Please contact us at copyright@packtpub.com with a link to the suspectedpirated material.We appreciate your help in protecting our authors, and our ability to bring youvaluable content.QuestionsYou can contact us at questions@packtpub.com if you are having a problem withany aspect of the book, and we will do our best to address it.[5]www.it-ebooks.info

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Preparing for WordPressDevelopmentSince you have picked up this book, you are likely to fall into one of two overallcategories: developers who are new to WordPress, or WordPress users keen to startor improve their WordPress development skills. No matter which camp you lie in,this book will help you down that path. This book will show you how to customizeWordPress using plugins by providing well-structured code and by explaininghow the code interacts with the WordPress application. It introduces a variety ofdevelopment techniques drawn from a range of real-world scenarios that will giveyou, the reader, a practical understanding of how to write, debug, and deployWordPress plugins.Together we will delve through a series of increasingly challenging topics coveringa range of scenarios that a developer is likely to encounter when developing andmaintaining a WordPress 3 site. While you may read the book from start to finish,each chapter strives to be a self-contained topic for easier reference.It is expected that the readers of this book have some knowledge of programmingconcepts and a working understanding of web applications, including HTML andbasic CSS. Familiarity with WordPress is also recommended.WordPress backgroundWordPress is a popular content management system (CMS), most renowned for itsuse as a blogging / publishing application. According to usage statistics tracker,BuiltWith (http://builtWith.com), WordPress is considered to be the most popularblogging software on the planet—not bad for something that has only been aroundofficially since 2003. It has always sought to allow its users to publish informationeasily, and although it can be used successfully for sites that are not blog-centric,running a blog has been a guiding star in WordPress' design since its inception.www.it-ebooks.info

Preparing for WordPress DevelopmentExtending WordPressLike many systems, WordPress may not do everything you want right out of the box.Instead, it focuses on a set of core features and allows for customizations in the form ofplugins, so if the built-in functionality doesn't meet your needs, your options are to: Find an existing third-party plugin Write your own plugin Look for another CMS entirelyIt is well worth your time to search for an existing solution if WordPress doesn'talready have the functionality that you require—chances are high that someoneout there has already done what you are trying to do. It may not be as much fun oras glamorous as developing your own shiny new code, but it is usually easier andfaster to cash in on the work others have done, just be aware that a lot of code in theWordPress repository is written by amateurs and it may contain bugs.If you do end up extending WordPress with your own plugin, and we hope you dosince you are reading this book, make sure that you are doing one of two things:either you are solving a problem that nobody has solved before, or you are comingup with a better mousetrap and re-solving a problem in a new and valuable way.Understanding WordPress architectureSpend a few minutes kicking the tires and you will become familiar with WordPress'features: Clean blog management Flexible permalink structure Easy search engine optimization (SEO) A simple package management tool The ability to update WordPress itself directly from the manager Versioning of drafts (so you don't lose data) A mature Ajax interface (lets you easily drag-and-drop widgets to customizeyour experience in the manager)This is a fine system, but it is a bit like listening to a car salesman—if you really wantto see how it performs, you should get your hands greasy and see what's under thehood. For developers, the real aspects of WordPress' customization and extensibilitylie in Templating and Plugins.[8]www.it-ebooks.info

Chapter 1TemplatingWordPress offers a templating system for implementing custom HTML and CSS,but it is not a templating system in the same sense as Smarty (http://www.smarty.net) or Perl's Template Toolkit. Instead, like many PHP CMSs (most notably Drupaland Joomla!), WordPress templates are simply PHP files that typically contain a mixof application logic and presentation code, for example, div id "footer" ?phpwp footer(); ? /div .Compare that with a Drupal template excerpt: div id "footer" ?php printrender( page['footer']); ? /div or with a MODx excerpt using Smartyplaceholders: div id "footer" [[*footer]] /div and you can get some ideaof the spectrum. Typically, the templates used in WordPress do not adhere to theModel-View-Controller (MVC) pattern, so they cause some developers to raise acritical eyebrow.Be aware that your WordPress templates contain PHP code and that they do execute,so it is naturally possible to "crash" your templates, or to have complex loops andlogical statements in them. As a developer, try your absolute best to separate logicfrom presentation and keep your templates as clean as possible. There are plenty ofWordPress theme files out there that contain a dizzying mess of PHP and HTML,which result in an unmaintainable no man's land. Designers won't touch thembecause they can't decipher the myriad if-statements and sloppy concatenations, anddevelopers won't touch them for the same reason, or perhaps because they containHTML and CSS that developers don't want to worry about. In the end, just try toavoid the numerous pitfalls that exist in this type of templating system.Introducing pluginsLike any good CMS, WordPress offers an application programming interface(API) for developers to perform common tasks in their plugins. Unlike many CMSs,however, the WordPress API is largely procedural: it exists mostly as a series ofglobally scoped functions and variables in the main namespace, so you have to beextra careful when naming your functions to avoid naming collisions. There arecertain tasks that are object oriented (OO), but there is a decent chance that you couldlook through a dozen WordPress plugins before encountering a class or an object. Incertain programming languages, such an arrangement is unusual if not impossible,but the PHP community in particular often offers procedural equivalents of objectoriented code.Opening up an existing WordPress plugin is a bit like going into a public restroom:it may be perfectly clean and hygienic, or it may be a rank and apoplectic mess offunctions, logic, and HTML. Just be prepared.[9]www.it-ebooks.info

Download from Wow! eBook www.wowebook.com Preparing for WordPress DevelopmentWhat is a plugin?The term "Plugin" is a bit ambiguous and WordPress' definition differsfrom other content management systems. In general, a WordPress pluginis any bit of code that extends the core functionality of WordPress. UnlikeExpression Engine, Drupal, or MODx, WordPress does not use differentterms such as "module", "snippet", or "add-on" to distinguish where orhow this extension occurs. In WordPress, they are all considered plugins.WordPress plugins use an event-driven architecture—anyone who has seen aJavaScript function triggered via an HTML "onClick" is familiar with this approach,but in WordPress, the events are typically ref

Chapter 1: Preparing for WordPress Development 7 WordPress background 7 Extending WordPress 8 Understanding WordPress architecture 8 Templating 9 Introducing plugins 9 Summarizing architecture 10 Tools for web development 11 WordPress 11 Mac 12 Windows 12 Text editor 12 Using an IDE 13 FTP client 14 MySQL client 14 Coding best practices 15