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WordPress Plugin Development Cookbook - Second Edition

By : Yannick Lefebvre

4.4 (12)

WordPress Plugin Development Cookbook

4.4 (12)

By: Yannick Lefebvre

Overview of this book

WordPress is a popular, powerful, and open Content Management System. Learning how to extend its capabilities allows you to unleash its full potential, whether you're an administrator trying to find the right extension, a developer with a great idea to enhance the platform for the community, or a website developer working to fulfill a client's needs. This book shows readers how to navigate WordPress' vast set of API functions to create high-quality plugins with easy-to-configure administration interfaces. With new recipes and materials updated for the latest versions of WordPress 4.x, this second edition teaches you 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 and execute custom user code. You will then see how to design administration panels, enhance the post editor with custom fields, store custom data, and modify site behavior based on the value of custom fields. You'll safely incorporate dynamic elements on web pages using scripting languages, 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.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

Preparing a Local Development Environment

Preparing a Local Development Environment

Introduction

Installing a web server on your computer

Downloading and configuring a local WordPress installation

Creating a local Subversion repository

Importing initial files to a local Subversion repository

Checking out files from a Subversion repository

Committing changes to a Subversion repository

Installing a dedicated code editor/text editor

Plugin Framework Basics

Plugin Framework Basics

Introduction

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 statistics tracking code in 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

User Settings and Administration Pages

User Settings and Administration Pages

Introduction

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

Adding menu items leading to external pages

Hiding items which users should not access from the default 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 network-level admin pages

The Power of Custom Post Types

The Power of Custom Post Types

Introduction

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

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 page title to include custom post data using plugin filters

Customizing Post and Page Editors

Customizing Post and Page Editors

Introduction

Capturing and displaying information using custom meta boxes

Displaying custom post data using filter functions

Hiding the Custom Field section in the post editor

Extending the post editor to allow users to upload files directly

Accepting User Content Submissions

Accepting User Content Submissions

Introduction

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

Customizing User Data

Customizing User Data

Introduction

Adding custom fields to the user editor

Processing and storing user custom data

Displaying new user data in user list page

Using custom user data in containing shortcode

Creating Custom MySQL Database Tables

Creating Custom MySQL Database Tables

Introduction

Creating new database tables

Deleting custom tables on plugin removal

Updating custom table structure on plugin upgrade

Displaying custom table data on an admin page

Inserting and updating records in custom tables

Deleting records from custom tables

Displaying custom database table data in shortcodes

Implementing a search function to retrieve custom table data

Importing data from a user file into custom tables

Leveraging JavaScript, jQuery, and AJAX Scripts

Leveraging JavaScript, jQuery, and AJAX Scripts

Introduction

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

Adding New Widgets to the WordPress Library

Adding New Widgets to the WordPress Library

Introduction

Creating a new widget in WordPress

Displaying configuration options

Validating configuration options

Implementing the widget display function

Adding a custom dashboard widget

Adding a custom widget to the network dashboard

Enabling Plugin Internationalization

Enabling Plugin Internationalization

Introduction

Changing the WordPress 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

Distributing Your Plugin on wordpress.org

Distributing Your Plugin on wordpress.org

Introduction

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

Preface

Developing plugins for WordPress is the next big thing for you if you are an administrator looking to enhance a personal site with custom functionality for which no plugin exists, a developer looking to enhance the WordPress platform with new ideas for the community, or a website designer building a specific project for a client. Learning how to create WordPress plugins will allow you to unleash the full potential of the most popular web content management system.

As an early WordPress adopter, before version 1.0 was out, I started building plugins to add functionality to my personal site. Once I got these new elements in place, I quickly realized that other users could benefit from these extensions, and started distributing them online. To this day, I always love hearing back from users of my creations and finding out how they have put them to use and what new functionality they think would make them even better.

While developing plugins might initially sound a little bit like black magic, this book shows you how easy creating plugins actually is through a series of step-by-step recipes. If you have previously added code to a theme's functions file, you may even be familiar with some of the mechanics explained in this book. With all of the information contained in this book, you will quickly be able to create your own plugins or dissect existing ones to add that extra bit of missing functionality that you require. Before you know, you'll be publishing your own creations to the official WordPress plugin repository!

Let's start learning how to cook up great WordPress plugins!

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