book

Building Web Apps with WordPress, 2nd Edition

by Brian Messenlehner, Jason Coleman

December 2019

Intermediate to advanced

543 pages

12h 52m

English

O'Reilly Media, Inc.

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Foreword
Preface
Who This Book Is ForWho This Book Is Not ForWhat You’ll LearnAbout the CodeConventions Used in This BookUsing Code ExamplesO’Reilly Online LearningHow to Contact UsAcknowledgments
1. Building Web Apps with WordPress
What Is a Website?What Is an App?What Is a Web App?Features of a Web AppMobile AppsProgressive Web AppsWhy Use WordPress?You Are Already Using WordPressContent Management Is Easy with WordPressUser Management Is Easy and Secure with WordPressPluginsFlexibility Is ImportantFrequent Security UpdatesCostResponses to Some Common Criticisms of WordPressWhen Not to Use WordPressYou Plan to License or Sell Your Site’s TechnologyAnother Platform Will Get You “There” FasterFlexibility Is Not Important to YouYour App Needs to Be Highly Real TimeWordPress as an Application FrameworkWordPress Versus Model-View-Controller FrameworksAnatomy of a WordPress AppWhat Is SchoolPress?SchoolPress Runs on a WordPress Multisite NetworkThe SchoolPress Business ModelMembership Levels and User RolesClasses Are BuddyPress GroupsAssignments Are a CPTSubmissions Are a (Sub)CPT for AssignmentsSemesters Are a Taxonomy on the Class CPTDepartments Are a Taxonomy on the Class CPTSchoolPress Has One Main Custom PluginSchoolPress Uses a Few Other Custom PluginsSchoolPress Uses the Memberlite Theme
2. WordPress Basics
WordPress Directory StructureRoot Directory/wp-admin/wp-includes/wp-contentWordPress Database Structurewp_optionsFunctions Found in /wp-includes/option.phpwp_usersFunctions Found in /wp-includes/…wp_usermetawp_postsFunctions Found in /wp-includes/post.phpwp_postmetaFunctions Found in /wp-includes/post.phpwp_commentsFunctions Found in /wp-includes/comment.phpwp_commentsmetaFunctions Found in /wp-includes/comment.phpwp_termsFunctions Found in /wp-includes/taxonomy.phpwp_termmetawp_term_taxonomy/wp-includes/taxonomy.phpwp_term_relationshipsHooks: Actions and FiltersActionsFiltersDevelopment and Hosting EnvironmentsWorking LocallyChoosing a Web HostDevelopment, Staging, and Production EnvironmentsExtending WordPress
3. Using WordPress Plugins
The General Public License, Version 2, LicenseInstalling WordPress PluginsBuilding Your Own PluginFile Structure for an App Plugin/adminpages//classes//css//js//images//includes//includes/lib//pages//services//scheduled//schoolpress.phpAdd-Ons to Existing PluginsUse Cases and ExamplesThe WordPress LoopWordPress Global VariablesFree PluginsAdmin ColumnsAdvanced Custom FieldsBadgeOSPosts 2 PostsMembersW3 Total CacheYoast SEOPremium PluginsGravity FormsBackupBuddyWP All ImportCommunity PluginsBuddyPress
4. Themes
Themes Versus PluginsWhere to Place Code When Developing AppsWhen Developing PluginsWhere to Place Code When Developing ThemesThe Template HierarchyPage TemplatesSample Page TemplateUsing Hooks to Copy TemplatesWhen Should You Use a Theme Template?Theme-Related WordPress FunctionsUsing locate_template in Your PluginsStyle.cssVersioning Your Theme’s CSS Filesfunctions.phpThemes and CPTsPopular Theme FrameworksWordPress Theme FrameworksNon-WordPress Theme FrameworksCreating a Child Theme for MemberliteIncluding Bootstrap in Your App’s ThemeMenusNavigation MenusDynamic MenusResponsive DesignDevice and Display Detection in CSSDevice and Feature Detection in JavaScriptDevice Detection in PHPFinal Note on Browser Detection
5. Custom Post Types, Post Metadata, and Taxonomies
Default Post Types and CPTsPagePostAttachmentRevisionsNavigation Menu ItemCustom CSSChangesetsoEmbed CacheUser RequestsReusable BlocksDefining and Registering CPTsregister_post_type( $post_type, $args );What Is a Taxonomy and How Should I Use It?Taxonomies Versus Post MetaCreating Custom Taxonomiesregister_taxonomy( $taxonomy, $object_type, $args )register_taxonomy_for_object_type( $taxonomy, $object_type )Using CPTs and Taxonomies in Your Themes and PluginsThe Theme Archive and Single Template FilesGood Old WP_Query and get_posts()Metadata with CPTsadd_meta_box( $id, $title, $callback, $screen, $context, $priority, $callback_args )Using Meta Boxes with the Block EditorCustom Wrapper Classes for CPTsExtending WP_Post Versus Wrapping ItWhy Use Wrapper Classes?Keep Your CPTs and Taxonomies TogetherKeep It in the Wrapper ClassWrapper Classes Read Better
6. Users, Roles, and Capabilities
Getting User DataAdd, Update, and Delete UsersHooks and FiltersWhat Are Roles and Capabilities?Checking a User’s Role and CapabilitiesCreating Custom Roles and CapabilitiesExtending the WP_User ClassAdding Registration and Profile FieldsCustomizing the Users Table in the DashboardPluginsTheme My LoginHide the Admin Bar from NonadministratorsPaid Memberships ProPMPro Register HelperMembersWP User Fields
7. Working with WordPress APIs, Objects, and Helper Functions
Shortcode APIShortcode AttributesNested ShortcodesRemoving ShortcodesOther Useful Shortcode-Related FunctionsWidgets APIBefore You Add Your Own WidgetAdding WidgetsDefining a Widget AreaEmbedding a Widget Outside of a Dynamic SidebarDashboard Widgets APIRemoving Dashboard WidgetsAdding Your Own Dashboard WidgetSettings APIDo You Really Need a Settings Page?Could You Use a Hook or Filter Instead?Use Standards When Adding SettingsIgnore Standards When Adding SettingsRewrite APIAdding Rewrite RulesFlushing Rewrite RulesOther Rewrite FunctionsWP-CronAdding Custom IntervalsScheduling Single EventsKicking Off Cron Jobs from the ServerUsing Server Crons OnlyWP MailSending Nicer Emails with WordPressFile Header APIAdding File Headers to Your Own FilesAdding New Headers to Plugins and ThemesHeartbeat API
8. Secure WordPress
Why It’s ImportantSecurity BasicsUpdate FrequentlyDon’t Use the Username “admin”Use a Strong PasswordExamples of Bad PasswordsExamples of Good PasswordsHardening WordPressDon’t Allow Admins to Edit Plugins or ThemesChange Default Database Tables PrefixMove wp-config.phpHide Login Error MessagesHide Your WordPress VersionDon’t Allow Logins via wp-login.phpAdd Custom .htaccess Rules for Locking Down wp-adminSSL Certificates and HTTPSInstalling an SSL Certificate on Your ServerWordPress Login and WordPress Administrator over SSLDebugging HTTPS IssuesAvoiding SSL Errors with the “Nuclear Option”Back Up Everything!Scan, Scan, Scan!Useful Security PluginsSpam-Blocking PluginsBackup PluginsFirewall/Scanner PluginsLogin and Password-Protection PluginsWriting Secure CodeCheck User CapabilitiesCustom SQL StatementsData Validation, Sanitization, and EscapingNonces

9. JavaScript Frameworks and Workflow
What Is ECMAScript?What Is ES6?What Is ES9?What Is ESNext?What Is Ajax?What Is JSON?jQuery and WordPressEnqueuing Other JavaScript LibrariesWhere to Put Your Custom JavaScriptAjax Calls with WordPress and jQueryManaging Multiple Ajax RequestsHeartbeat APIWordPress Limitations with Asynchronous ProcessingJavaScript FrameworksBackbone.jsReact
10. WordPress REST API
What Is a REST API?APIRESTJSONHTTPWhy Use the WordPress REST API?Using the WordPress REST API V2DiscoveryAuthenticationRoutes and EndpointsRequestsResponsesAdding Your Own Routes and Endpointsregister_rest_route( $namespace, $route, $args, $override );Setting Up the WordPress Single Sign-On PluginAdding the /wp-sso/v1/check RouteBundling Basic Authentication with Our PluginUsing the Endpoint We Set Up to Check User CredentialsPopular Plugins Using the WordPress REST APIWooCommerceBuddyPressPaid Memberships Pro
11. Project Gutenberg, Blocks, and Custom Block Types
The WordPress EditorThe Classic Editor PluginUsing Blocks for Content and DesignUsing Blocks for FunctionalityCreating Your Own BlocksMinimal Block ExampleUsing Custom Blocks to Build App ExperiencesEnabling the Block Editor in Your CPTsBlock CategoriesThe Homework BlocksLimiting Blocks to Specific CPTsLimiting CPTs to Specific BlocksBlock TemplatesSaving Block Data to Post MetaTipsEnable WP_SCRIPT_DEBUGUse filemtime() for the Script VersionMore TipsLearn JavaScript, Node.js, and React More Deeply
12. WordPress Multisite Networks
Why Multisite?Why Not Multisite?Multisite AlternativesMultiple Authors or Categories on the Same WordPress SiteCustom Post TypesTotally Separate SitesUse a WordPress Maintenance ServiceMultitenancySetting Up a Multisite NetworkManaging a Multisite NetworkDashboardSitesUsersThemesPluginsSettingsUpdatesMultisite Database StructureNetworkwide TablesIndividual Site TablesShared Site TablesDomain MappingRandom Useful Multisite PluginsGravity Forms User Registration Add-OnMember Network Sites Add-On for Paid Memberships ProMore Privacy OptionsMultisite Global MediaMultisite Plugin ManagerMultisite Global SearchMultisite Robots.txt ManagerNS Cloner: Site CopierWP Multi NetworkBasic Multisite Functionality$blog_idis_multisite()get_current_blog_id()switch_to_blog( $new_blog )restore_current_blog()get_blog_details( $fields = null, $get_all = true )update_blog_details( $blog_id, $details = array() )get_blog_status( $id, $pref )update_blog_status( $blog_id, $pref, $value )get_blog_option( $id, $option, $default = false )update_blog_option( $id, $option, $value )delete_blog_option( $id, $option )get_blog_post( $blog_id, $post_id )add_user_to_blog( $blog_id, $user_id, $role )wpmu_delete_user( $user_id )create_empty_blog( $domain, $path, $weblog_title, $site_id = 1 )Functions We Didn’t Mention
13. Localizing WordPress Apps
Do You Even Need to Localize Your App?How Localization Is Done in WordPressDefining Your Locale in WordPressText DomainsSetting the Text DomainPrepping Your Strings with Translation Functions__( $text, $domain = “default” )_e( $text, $domain = “default” )_x( $text, $context, $domain = “default” )_ex( $title, $context, $domain = “default” )Escaping and Translating at the Same TimeCreating and Loading Translation FilesOur File Structure for LocalizationGenerating a .pot FileCreating a .po FileCreating a .mo FileGlotPressUsing GlotPress for Your WordPress.org Plugins and ThemesCreating Your Own GlotPress Server
14. WordPress Optimization and Scaling
TermsOrigin Versus EdgeTestingWhat to TestChrome Debug BarThe WordPress Site Health ToolApache BenchSiegeW3 Total CachePage Cache SettingsMinifyDatabase CachingObject CacheCDNsGZIP CompressionHostingWordPress-Specific HostsRolling Your Own ServerSelective CachingThe Transient APIMultisite TransientsUsing JavaScript to Increase PerformanceCustom TablesBypassing WordPress
15. Ecommerce
Choosing a PluginWooCommercePaid Memberships ProEasy Digital DownloadsPayment GatewaysMerchant AccountsSetting Up SaaS with Paid Memberships ProThe SaaS ModelStep 0: Establishing How You Want to Charge for Your AppStep 1: Installing and Activating Paid Memberships ProStep 2: Setting Up the LevelStep 3: Setting Up PagesStep 4: Choosing Payment SettingsStep 5: Choosing Email SettingsStep 6: Choosing Advanced SettingsStep 7: Locking Down PagesStep 8: Customizing Paid Memberships Pro
16. Mobile Apps Powered by WordPress
Mobile App Use CasesNative and Hybrid Mobile AppsWhat Is a Native Mobile App?What Is a Hybrid Mobile App?Why Hybrid over Native?CordovaIonic FrameworkApp WrapperAppPresser
17. PHP Libraries, Web Service Integrations, and Platform Migrations
PHP LibrariesImage Generation and ManipulationPDF GenerationGeolocation and GeotargetingFile Compression and ArchivingDeveloper ToolsExternal APIs and Web ServicesElasticsearchElasticPress by 10upGoogle VisionGoogle MapsGoogle TranslateTwilioOther Popular APIsMigrationsHost MigrationsPlatform MigrationsCreate a Data Mapping Guide
18. The Future
Where We’ve BeenThe REST APIWordPress Plugins Will Focus More on APIsHeadless WordPressGraphQLGutenbergThe Administrator Interface Will Move to React/GutenbergGutenberg Will Power a Frontend Editing Experience for WordPressBlock Templates Will Replace ThemesBlocks Will Replace PluginsWordPress Market Share Will Increase and DecreaseWordPress Will Become a More Popular Platform for Mobile DevelopmentWordPress Will Continue to Be Useful for Developing Apps of All Kinds
Index

Overview

WordPress is much more than a blogging platform. If you have basic PHP, HTML, CSS, and JavaScript experience you can use WordPress to develop fast, scalable, secure, and highly customized web apps, mobile apps, web services, and multisite networks of websites. Along with core WordPress functions and database schema, you’ll learn how to build custom plugins, themes, and services for just about any kind of web or mobile application.

In this updated second edition, Brian Messenlehner and Jason Coleman cover new features and functionality added to WordPress up to version 5.4. All code examples in the book are available on GitHub.

Compare WordPress with traditional app development frameworks
Use themes for views and plugins for backend functionality
Get suggestions for choosing or building WordPress plugins
Register custom post types (CPTs) and taxonomies
Manage user accounts and roles, and access user data
Build asynchronous behaviors with jQuery
Use WordPress to develop mobile apps for iOS and Android
Integrate PHP libraries, external APIs, and web service plugins
Collect payments through ecommerce and membership plugins
Learn how to speed up and scale your WordPress app
Extend the WordPress REST API and create custom endpoints
Learn about WordPress Gutenberg blocks development

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