This document provides an overview of plugin development for beginners. It discusses reasons for making a plugin such as adding functionality or contributing solutions to the community. Software licenses like GPL are expected to be included with plugins. Simple ways to start include single PHP files or using a boilerplate. Examples of procedural and object-oriented single file plugins are provided. Best practices for folder structure in multi-file plugins and avoiding class name collisions are covered. Resources for learning plugin development are listed.

1. Plugin
Development for
Beginners
By Joe Cartonia

2. About me
Name: Joe Cartonia
GitHub: https://github.com/cssjoe
Twitter: @joemotocss
I was born in Buffalo, living in Virginia Beach since 2007, and working as a WordPress
plugin and API developer for BoldGrid since 2014. Technology has always been a major
interest of mine since the first grade. I also enjoy traveling, motorsports, snowboarding,
playing guitar, and spending time at the beach.

3. Why make a plugin?
● Add functionality to your website
○ There may not be a plugin available to satisfy your needs
○ Other plugins may not suffice or may be too complicated
● Create a useful plugin, intending to publish in the WordPress.org directory.
○ Contribute open source solutions to the community
● Make a plugin for a commercial or private service
○ For sale or subscription
○ If the license is not GPL, then it cannot be on WordPress.org.

4. Software licenses
A software license is expected to be included with plugins. In most cases, GPL (General
Public License) is used; the same open source license that WordPress core uses. This
means that everyone is free to use and redistribute the plugin, in a modified or
unmodified form.
License specification examples: GPL-2.0-or-later, GPL-2.0+, GPL2, GPL3, MIT
Information on licenses:
● https://developer.wordpress.org/plugins/the-basics/including-a-software-license/
● https://www.gnu.org/licenses/gpl.html
● https://choosealicense.com/

5. Simple ways to start developing a plugin
● Single PHP file
○ For simple/basic functionality
○ Quick and easy
○ https://developer.wordpress.org/plugins/the-basics/header-requirements/
■ Start with a main plugin file header
● Multiple files under a directory structure
○ For more advanced functionality
○ Usually requires more of a time investment
○ Better organization of code; readability and easier to maintain.
○ Allows code to be modular
● Boilerplate
○ For more advanced developers
○ Similar to multiple files, but provides a head start to creating the structure.
○ Online generators, such as: https://wppb.me/
○ Examples on GitHub: https://github.com/devinvinson/WordPress-Plugin-Boilerplate/

6. A single file plugin
using procedural
This is a small PHP file containing everything needed
to convert a shortcode to a content block.
A shortcode is registered and mapped to a callback
function, which is defined in the global scope. The
name is prefixed, to help prevent duplicate function
declarations / name collision.
https://developer.wordpress.org/plugins/the-basics/
best-practices/#procedural
https://github.com/cssjoe/my-signature/tree/0.1.0

7. A single file plugin
using Object Oriented
Programming (OOP)
This is a small PHP file containing everything needed
to convert a shortcode to a content block.
A class definition is used to confine the functions and
variables to the scope of a class. It is recommended
to avoid littering the global space.
https://developer.wordpress.org/plugins/the-basics/best-prac
tices/#oop
https://github.com/cssjoe/my-signature/tree/1.0.0

8. Avoiding class name collisions
Class names can be defined different ways. They should be unique in the global space.
● Using a unique prefix
○ Example: class My_Plugin_Name_Some_Class_Name {}
○ Accessed globally using My_Plugin_Name_Some_Class_Name
● Using a namespace
○ Example: namespace PluginNameCategory;
class My_Class {}
○ Accessed globally using PluginNameCategoryMy_Class
○ https://www.php.net/manual/en/language.namespaces.rationale.php

9. A plugin with multiple
files and directories
This is a group of directories containing the files
needed to convert a shortcode to a content block.
https://developer.wordpress.org/plugins/the-basi
cs/best-practices/#folder-structure
https://github.com/cssjoe/my-signature/tree/2.0.0

10. The example plugin in action
Left side: A shortcode
“[my-signature]” is added to a page
in the wp-admin post and page
editor.
Right side: A preview of the page contains the
markup inserted from the plugin.

11. Resources available
WordPress.org
● Make WordPress Plugins: https://make.wordpress.org/plugins/
● Plugin Handbook: https://developer.wordpress.org/plugins/
● Plugin Directory: https://developer.wordpress.org/plugins/wordpress-org/
Code reference
● https://developer.wordpress.org/reference/
● http://www.php.net/
Making WordPress Slack Workspace
● https://wordpress.slack.com/messages/pluginreview
WordPress Meetups
● https://www.meetup.com/topics/wordpress/

12. Q & A
Please ask any questions that you may have.
I will try to answer all questions in the time that we have left.

13. Thank you!
I would like to thank everyone for attending.
The plugin examples used here are available on GitHub: https://github.com/cssjoe
This slideshow and others are available on SlideShare.net: https://www.slideshare.net/JoeCartonia
Please follow me on Twitter: @joemotocss