This is a presentation from WordCamp Victoria 2013 where I show power users and novice developers how to get started with plugin development. I think a lot of people don’t realize how easy it is to get started with plugin development or just how small and simple can be. It doesn’t require 100s of lines of code… Many WordPress tutorials out there talk about copy this or that to your functions.php file in your theme. However, it’s just as easy to create your own functionality plugin; which makes for easier to maintain code in the future that isn’t theme dependant. I begin this talk with the basics of what a plugin is and how it’s structured. I then explain the hooks (actions and filters API), followed by a very simplistic demo. I then give some pro tips and talk about some of the most commonly used WordPress APIs in plugins, as well as promote coding standards. A second more in-depth demo is then presented. Finally, I discuss security in plugins and share some resources for developers and users to further learn from.

1. Plugin
Development
- Joey Kudish
http://slides.jkudish.com
Friday, 11 January, 13

2. About me
• WordPress developer since 2007
• Initially built sites for a variety of clients
• Freelance plugin development
• Code Wrangler at WordPress.com / Automattic
since May 2011
• Originally from Montreal, moved to Vancouver
in 2011
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4. What’s a
plugin?
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5. A plugin extends or
modi!es WordPress
to do something it
didn’t previously do
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6. Themes can act as
plugins. Oh and there’s
mu-plugins too.
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7. Plugins can be
huge...
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8. ... or tiny.
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9. What’s in a plugin?
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10. Where does it
go?
wp-content/plugins/[plugin_name]
or wp-content/mu-plugins/
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11. In order to “hook”
into WordPress, we
use action and !lter
hooks
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12. Action hooks allow
you to add your own
code to WordPress’
call stack
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13. Filter hooks allow
you to modify an
existing variable or
piece of information
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14. Demo time
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15. Let’s add Google
Webmaster Tools
veri!cation to our site
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19. Finding hooks
• WordPress.org Codex (http://
codex.wordpress.org/)
• http://adambrown.info/p/wp_hooks
• Debug Bar + Debug Bar Action Hooks plugin
(http://wordpress.org/extend/plugins/debug-bar-
action-hooks/)
• Search core (use your IDE or a command line
tool like ack)
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20. Some pro tips
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21. Use built-in APIs,
don’t re-invent the
wheel
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22. Use WordPress coding
standards
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23. Be nice to other devs.
Namespace your classes
and functions. Leave
hooks for others.
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24. Demo time
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29. hey that’s the
!le we want to hook
into
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34. Let’s create our
plugin
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43. It works, now let’s
have some fun
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48. Finished plugin
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49. A word on
Security
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50. don’t trust
users
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51. sanitize input,
escape output
http://codex.wordpress.org/Data_Validation
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52. protect users from
malicious attacks,
use nonces to
validate user actions
http://codex.wordpress.org/WordPress_Nonces
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53. Plugin
Distribution
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57. Further
reading
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61. http://www.wrox.com/WileyCDA/WroxTitle/ http://www.packtpub.com/wordpress-plugin-
Professional-WordPress-Plugin- development-cookbook/book
Development.productCd-0470916222.html
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62. Thanks!
Q&A
http://slides.jkudish.com
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