Book Image

WordPress Plugin Development Cookbook - Third Edition

By : Yannick Lefebvre
Book Image

WordPress Plugin Development Cookbook - Third Edition

By: Yannick Lefebvre

Overview of this book

WordPress is one of the most widely used, powerful, and open content management systems (CMSs). Whether you're a site owner trying to find the right extension, a developer who wants to contribute to the community, or a website developer working to fulfill a client's needs, learning how to extend WordPress' capabilities will help you to unleash its full potential. This book will help you become familiar with API functions to create secure plugins with easy-to-use administration interfaces. This third edition contains new recipes and up-to-date code samples, including new chapters on creating custom blocks for the block editor and integrating data from external sources. From one chapter to the next, you’ll learn how to create plugins of varying complexity, ranging from a few lines of code to complex extensions that provide intricate new capabilities. You'll start by using the basic mechanisms provided in WordPress to create plugins, followed by recipes covering how to design administration panels, enhance the post editor with custom fields, store custom data, and even create custom blocks. You'll safely incorporate dynamic elements into web pages using scripting languages, learn how to integrate data from external sources, and build new widgets that users will be able to add to WordPress sidebars and widget areas. By the end of this book, you will be able to create WordPress plugins to perform any task you can imagine.

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Table of Contents (15 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Download the example code files
Download the color images
Conventions used
Sections
Get in touch
Share Your Thoughts
1
Chapter 1: Preparing a Local Development Environment
Chapter 1: Preparing a Local Development Environment
Technical requirements
Installing a local web server on your computer
Creating a local version control repository
Installing a dedicated code editor/text editor
Free Chapter
2
Chapter 2: Plugin Framework Basics
Chapter 2: Plugin Framework Basics
Technical requirements
Creating a plugin file and header
Adding output content to page headers using plugin actions
Using WordPress path utility functions to load external files and images
Modifying the site generator meta tag using plugin filters
Adding text after each item's content using plugin filters
Inserting link tracking code in the page body using plugin filters
Troubleshooting coding errors and printing variable content
Creating a new simple shortcode
Creating a new shortcode with parameters
Creating a new enclosing shortcode
Loading a style sheet to format plugin output
Writing plugins using object-oriented PHP
3
Chapter 3: User Settings and Administration Pages
Chapter 3: User Settings and Administration Pages
Technical requirements
Creating default user settings on plugin initialization
Storing user settings using arrays
Removing plugin data on deletion
Creating an administration page menu item in the settings menu
Creating a multi-level administration menu
Rendering the admin page contents using HTML
Processing and storing plugin configuration data
Displaying a confirmation message when options are saved
Adding custom help pages
Rendering the admin page contents using the Settings API
Accessing user settings from action and filter hooks
Formatting admin pages using meta boxes
Splitting admin code from the main plugin file to optimize site performance
Storing style sheet data in user settings
Managing multiple sets of user settings from a single admin page
Creating a network-level plugin with admin pages
4
Chapter 4: The Power of Custom Post Types
Chapter 4: The Power of Custom Post Types
Technical requirements
Creating a custom post type
Adding a new section to the custom post type editor
Displaying single custom post type items using a custom layout
Tailoring search output for custom post type items
Displaying custom post type data in shortcodes
Adding custom categories for custom post types
Adding custom fields to categories
Hiding the category editor from the custom post type editor
Displaying additional columns in the custom post list page
Adding filters for custom categories to the custom post list page
Adding Quick Edit fields for custom categories
Updating the page title to include custom post data using plugin filters
5
Chapter 5: Customizing Post and Page Editors
Chapter 5: Customizing Post and Page Editors
Technical requirements
Capturing and displaying information using custom meta boxes
Displaying custom post data using filter functions
Hiding the Custom Fields section in the post editor
Extending the post editor to attach custom files with the media uploader
6
Chapter 6: Extending the Block Editor
Chapter 6: Extending the Block Editor
Technical requirements
Setting up a block development environment and creating a simple block
Creating an editable blockquote block
Creating a new WordPress REST endpoint
Creating a server-side rendering block that leverages an existing shortcode
7
Chapter 7: Accepting User Content Submissions
Chapter 7: Accepting User Content Submissions
Technical requirements
Creating a client-side content submission form
Saving user-submitted content in custom post types
Sending email notifications upon new submissions
Implementing a CAPTCHA on user forms using an online service
Using a local library to implement a CAPTCHA on user forms
8
Chapter 8: Customizing User Data
Chapter 8: Customizing User Data
Technical requirements
Adding custom fields to the user editor
Processing and storing custom user data
Displaying new user data on the user list page
Using custom user data in an enclosing shortcode
9
Chapter 9: Leveraging JavaScript, jQuery, and AJAX Scripts
Chapter 9: Leveraging JavaScript, jQuery, and AJAX Scripts
Technical requirements
Safely loading jQuery onto WordPress web pages
Displaying a pop-up dialog using the built-in ThickBox plugin
Controlling pop-up dialog display using shortcodes
Displaying a calendar day selector using the Datepicker plugin
Adding tooltips to admin page form fields using the TipTip plugin
Using AJAX to dynamically update partial page contents
10
Chapter 10: Adding New Widgets to the WordPress Library
Chapter 10: Adding New Widgets to the WordPress Library
Technical requirements
Creating a new widget in WordPress
Displaying widget configuration options
Validating widget configuration options
Adding a custom dashboard widget
Adding a custom widget to the network dashboard
11
Chapter 11: Fetching, Caching, and Regularly Updating External Site Data
Chapter 11: Fetching, Caching, and Regularly Updating External Site Data
Technical requirements
Displaying RSS items from an external feed
Optimizing plugin performance by storing external data using transients
Scheduling plugin data updates using WP-Cron
12
Chapter 12: Enabling Plugin Internationalization
Chapter 12: Enabling Plugin Internationalization
Technical requirements
Changing the WordPress site language configuration
Adapting default user settings for translation
Making admin page code ready for translation
Modifying shortcode output for translation
Translating text strings using Poedit
Loading a language file in the plugin initialization
13
Chapter 13: Distributing Your Plugin on WordPress.org
Chapter 13: Distributing Your Plugin on WordPress.org
Technical requirements
Creating a README file for your plugin
Applying for your plugin to be hosted on WordPress.org
Uploading your plugin using Subversion
Providing plugin banner and thumbnail images
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14
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Adding custom fields to the user editor

Similar to the taxonomy editor, the user editor allows developers to add extra fields through action hooks. This task is facilitated by using the same HTML structure, whether a new user is being created or an existing one is modified.

Getting ready

To create a complete plugin with a stylesheet and administration panel, you should have already followed the Storing stylesheet data in user settings recipe in Chapter 3, User Settings and Administration Pages, to have a starting point for this recipe. Alternatively, you can get the resulting plugin code directory (ch3/ch2-private-item-text/*) from the book's GitHub page and rename ch2-private-item-text-v2.php to ch2-private-item-text.php.

It is also possible to start fresh and create a new empty plugin file and follow this chapter's recipes by making a folder called ch2-private-item-text in your plugin directory with a text file called ch2-private-item-text.php, and only adding...

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