Quick and basic presentation about how to get started writing WordPres

1. How to Write a
WordPress Plugin
Baltimore WordPress Meetup • September 19,
2011

2. What is a plugin?
Written in PHP
Adds functionality
without affecting core
code
Plugin API

3. Hooks: Actions &
Filters

4. Actions
Hey, WP! I’d like to do this
when you do that...
Calls a function that performs an
action, possibly with some data
given by WP

5. Actions
add_action( $hook_name, $function );
add_action(‘wp_head’, ‘my_custom_js’);
add_action(‘wp_head’, array(
$some_object, ‘my_custom_js_method’)
));

6. Actions
init
wp_head
save_post

7. Filters
Hey, WP! I’d like to change a
value that you’re returning/
using...
Calls a function that returns a final

8. Filters
add_filter( $hook_name, $function );
add_filter(‘the_content’, ‘my_content_filter’);
add_filter(‘the_content’, array(
$some_object, ‘my_content_method)
));

9. Filters
the_title
the_content
wp_email_from

10. Getting Started
PHP file or folder
containing PHP file
Javascript, CSS, etc.
/wp-content/

11. Plugin Information
<?php
/*
Plugin Name: My Simple Plugin
Plugin URI: http://theandystratton.com/my-plugin
Description: Does something awesome.
Version: 1.0
Author: theandystratton
Author URI: http://theandystratton.com
License: GPL2
*/

12. Info Shows in Admin
UI

13. Don’t Just Drop
Code
WordPress includes plugins
while initializing
Coding without hooking into
actions/filters = explosion

14. Starting to Code
What do you want to do?
I want to add my personal
signature to all posts.

15. Starting to Code
What does my plugin do?
Filter the content of all
posts and append my
signature.

16. Some Code
Hey WP! When you’re
processing standard content,
call this function!

17. Take the value WP provides us, add
my signature, give it back.

18. It’s as easy as that.

19. But we can
complicate things...

20. Archives, Listings,
etc.
Oops. I mean, I only want it
to add my signature to the
single post, not listings/
archives.

21. Archives, Listings,
etc.
What do you want to do
now?
Filter the content of all posts
and append my signature

22. IF we’re on a single post page,
THEN add my signature.

23. But we can
complicate things...

24. Post Type Content
Oops. I have a custom post
type called “Products,” and
it’s adding my signature to
those, too.

25. IF we’re on a single blog post
page, THEN add my signature.

27. Getting More
Advanced

28. Using Objects
Avoid tons of
prefixed functions
Use a prefixed class to hold
all your actions/filters

29. Using Objects

30. Do All Kinds of Fun
Stuff

31. Plugins Do Way
More
Custom Post Types
Shortcodes
Metaboxes and metadata
management

32. Plugins Do Way
More
Settings Pages
Settings Fields
Incorporate Internationalization

33. Plugins Do Way
More
Redirect requests
Modify Rewrite Rules
Emulate CRON jobs (wp-
cron.php)

34. Going Public

35. Get in the
Repository
Submit your plugin code
http://wordpress.org/extend/plugins/
about/
http://wordpress.org/extend/plugins/
about/faq/

36. Get in the
Repository
Readme.txt
http://wordpress.org/extend/plugins/
about/readme.txt

37. Get in the
Repository
Subversion access &
management
Support URL?
Update within 2 years or hide

38. More Resources
“Writing a Plugin”
http://codex.wordpress.org/
Writing_a_Plugin
“WordPress Coding
Standards”
http://codex.wordpress.org/
WordPress_Coding_Standards

39. Google Works Great

40. Keep It Simple Stupid.

41. Code is poetry.

42. Thanks.