The document is a presentation outline from WordCamp Birmingham discussing WordPress's extensibility and its developer APIs, which include themes, plugins, and various functionalities such as actions, filters, and metadata. The presenter, Dougal Campbell, acknowledges that the slide deck is incomplete but plans to provide a more thorough version at WordCamp Atlanta. Key features of WordPress highlighted include the ability for plugins to modify content, integrate third-party data, and manage user roles and access.

1. CSI:
Getting Into the Guts
WordCamp Birmingham, January 14, 2012

2. CSI:
Getting Into the Guts
WordCamp Birmingham, January 14, 2012

3. Version 0.5
Please note that due to unforeseen events, I did not
complete this slide deck to my satisfaction before
presenting it at WordCamp Birmingham.
I will be doing this presentation again at WordCamp
Atlanta, with an improved version of these slides. At that
time, I will replace this presentation with the new,
improved version which will contain more concrete
developer information, code samples, and more
comprehensive pointers to resources.
Thank you for your understanding.
-- Dougal

4. WordPress
Rocks!

5. WordPress
Rocks!
Why?

6. Extensibility
WordPress can do just about any
freaking thing you can think of

7. Extensibility

8. Extensibility
✤ Rich developer APIs

9. Extensibility
✤ Rich developer APIs
✤ Themes

10. Extensibility
✤ Rich developer APIs
✤ Themes
✤ Plugins

11. API

12. API
✤ Application Programming
Interface

13. API
✤ Application Programming
Interface
✤ “...a source code based
specification intended to be
used as an interface by
software components to
communicate with each
other.” – Wikipedia

14. What kind of APIs?
✤ Pluggable functions
✤ Hooks
✤ Actions and Filters
✤ Metadata
✤ Post meta, User meta, Comment meta, Site Options
✤ Custom Javascript and CSS

15. Pluggable
Functions
Login/Cookie/User info
Email notifications, wp_mail()
Security: nonces, password salts &
hashes
Avatars
Display of revision diffs

16. Themes
✤ Sidebars and Widgets
✤ Custom Headers and
Backgrounds
✤ Custom Post Types and
Taxonomies

17. Plugins

18. Plugins
✤ Plugins can do... practically anything:

19. Plugins
✤ Plugins can do... practically anything:
✤ Modify posts/pages

20. Plugins
✤ Plugins can do... practically anything:
✤ Modify posts/pages
✤ Integrate 3rd party data (Twitter, Facebook, etc.)

21. Plugins
✤ Plugins can do... practically anything:
✤ Modify posts/pages
✤ Integrate 3rd party data (Twitter, Facebook, etc.)
✤ Extend user info

22. Plugins
✤ Plugins can do... practically anything:
✤ Modify posts/pages
✤ Integrate 3rd party data (Twitter, Facebook, etc.)
✤ Extend user info
✤ Use Roles & Capabilities to control access to features

23. Plugins
✤ Plugins can do... practically anything:
✤ Modify posts/pages
✤ Integrate 3rd party data (Twitter, Facebook, etc.)
✤ Extend user info
✤ Use Roles & Capabilities to control access to features
✤ Create workflows (e.g., EditFlow plugin)

24. Plugins
✤ Plugins can do... practically anything:
✤ Modify posts/pages
✤ Integrate 3rd party data (Twitter, Facebook, etc.)
✤ Extend user info
✤ Use Roles & Capabilities to control access to features
✤ Create workflows (e.g., EditFlow plugin)
✤ Alternative login systems (LDAP, SSO)

25. Plugins
✤ Plugins can do... practically anything:
✤ Modify posts/pages
✤ Integrate 3rd party data (Twitter, Facebook, etc.)
✤ Extend user info
✤ Use Roles & Capabilities to control access to features
✤ Create workflows (e.g., EditFlow plugin)
✤ Alternative login systems (LDAP, SSO)
✤ The sky’s the limit!

26. Actions
Actions are events
Use them to DO something, rather
than to CHANGE something

27. Actions
plugins_loaded()
setup_theme()
wp_init()
template_redirect()
wp_head()
wp_footer()
http://andy.wordpress.com/2008/10/30/wordpress-include-stack/

28. Filters
Modify existing content
<?php
add_filter( ‘the_content’, ‘lolify’ );
function lolify( $text_in ) {
$text out = do_cool_stuff( $text_in );
return $text_out;
}
?>

29. Metadata
Lets you add additional details beyond
what WordPress provides out-of-the-
box.

30. Metadata
✤ “Data about Data”
Lets you provide additional
details that may or may not be
visible on the site.

31. Putting it
together
✤ codex.wordpress.org
✤ make.wordpress.org
✤ wpdevel.wordpress.com

32. Who are you?
Dougal Campbell
@dougal
dougal.us /
dougal.gunters.org
dougal.campbell@gmail.com