This document outlines best practices for developing a WordPress plugin from scratch. It discusses code readability standards, references for plugin development, and creating a basic plugin structure. It then describes building a sample "Fancy" gallery plugin to demonstrate integrating Fancybox functionality into the WordPress gallery. Key aspects covered include hooking into WordPress actions and filters, implementing a plugin options page using the Settings API, enqueueing scripts and styles, and modifying the gallery link output. The document aims to teach plugin development fundamentals and best practices.

1. Best practices for
plugin development
Create a WordPress plugin from
scratch

2. Andrea Sciamanna
present
● Lead developer for WPML
● responsible and active
developer of the WPML
plugin and add-ons
past
● Web and desktop application
developer (mostly using .net
framework)

3. Agenda
● Quick introduction about:
a. code readability
b. documentation
c. patterns
● Some references
● Creating a WordPress plugin from scratch
● (time allowing) Introducing IDEs and OOP

4. Code readability
1. Use coding standards
a. Use WordPress PHP Coding Standards: http://goo.
gl/FTMm0a
b. Comment with PhpDOC: http://www.phpdoc.org
c. Don't repeat yourself (DRY): http://blog.codinghorror.
com/curlys-law-do-one-thing
d. Don’t go crazy trying to follow standards: just get used
to them.

5. References
● WordPress Codex: http://codex.wordpress.org
● Stack Overflow: http://stackoverflow.com
○ WordPress Development: http://wordpress.
stackexchange.com
● Google: seriously, do I need to tell you?

6. Create a WordPress
plugin from scratch

7. A “Fancy” plugin for your galleries
Integrate Fancybox in the standard WordPress
gallery.

8. Planned Functionalities
● Show images in a Fancybox/lightbox, rather
than opening them in a different page
● Do not interfere with the active theme
● Make it “SEO proof”
● Pseudo-Watermark images without modifying
them
● Allow some customization

9. Goals
● Learn how to:
○ enqueue scripts and styles
○ use actions and filters
○ use WordPress Settings API
● Learn best practices, of course!
● ...and the Fancybox plugin

10. Standard plugin structure
● Single file: unique file name (my-own-plugin.
php)
● Complex structure:
○ unique folder name (/wp-content/plugins/my-own-
plugin/)
○ bootstrap script: plugin.php or any name
● Main plugin file: Standard Plugin Information
● readme.txt file

11. Skeleton

12. Main plugin file
● Define useful constants, for later use:
○ Plugin version
○ Plugin path
○ Plugin folder
○ Plugin URL
● Include dependencies
○ Shared functions
○ Core class
○ Options class
➔ Remember to namespace
your functions, by either
using unique plugins, or
unique class names
➔ Do not use actual PHP
namespaces!

13. Hooks
● What are they?
○ Actions -> They do things
○ Filters -> They return something
● How they must be used?
○ “Hook” a filter, or action to a custom function
● When?
○ At the right time: it’s a bit tricky and needs practices,
some cheat sheet, or asking the community

14. Hook to some actions and filters
● The loader class: why?
○ Decoupling functionalities
○ Specialized classes
● Hook to actions:
○ ‘plugins_loaded’ -> the actual entry point (usually)
○ ‘wp_enqueue_scripts’ -> scripts and CSS goes here
● Hook to filters:
○ ‘wp_get_attachment_link’

15. Implement hooks
● Hook to actions
○ Add scripts and styles
■ Main script and styles
■ Fancybox, helpers and more
■ Pass data to scripts: wp_enqueue_script()
● Hook to filters
○ Tweak the gallery item link

16. Plugin options definitions and handling
● Implement plugin options
○ A new class => a new file
○ The options loader class

17. WP Settings API
● WP Settings API
○ register_setting()
○ add_settings_section()
○ add_settings_field()
○ callbacks
○ options_do_page
● Some thoughts about the APIs:
○ Counterintuitive
○ Old
Honestly, we ought to take the time to learn the Settings API however the steep the learning curve,
and start working with it. It is the definitive way to go about creating options pages, and it is the current
version of the API that we have available.
Tom McFarlin (http://tommcfarlin.com/wordpress-settings-api-wrapper)

18. Plugin options page
● Show the plugin options page
○ OTGS_Fancybox_Gallery_Options::get_setting static
method: why is static?
○ Add a menu item in “Settings” menu
○ Add some javascript and enqueue the script in the
back-end

19. Refine the main class
● Handle plugin options
● Take advantage of $wp_object_cache in
OTGS_Fancybox_Gallery::
get_attachment_link

20. The main gallery.js
● Do not use $ (in WordPress)!
● Implement jquery.fancybox()
● Cache jQuery elements
● Play with plugin options

21. Test it

22. Questions?