Writing Your First WordPress Plugin

Writing Your First Plugin by Mark Jaquith @markjaquith markjaquith.com Saturday, August 21, 2010

Assumptions • You know PHP syntax • You’re targeting PHP 5 Saturday, August 21, 2010

What I want you to learn • Plugins change what WordPress does • They rely on the concepts of actions and ﬁlters • There are numerous internal WordPress APIs for you to use Saturday, August 21, 2010

What is a Plugin? • PHP code that sits in separate ﬁles • Integrates tightly with WordPress • Can add, alter, or remove functionality Saturday, August 21, 2010

Where? • wp-content/plugins/name.php • wp-content/plugins/folder/name.php • WordPress only looks one level deep • It looks for .php ﬁles with a plugin header Saturday, August 21, 2010

Plugin Header “Plugin Name” is required. Saturday, August 21, 2010

Basic Structure • Build some stuff • Tell WordPress to use that stuff when WordPress does certain stuff Saturday, August 21, 2010

Actions • Triggered when various things happen in WordPress core • “Wakes up” code you’ve registered against that action Saturday, August 21, 2010

Actions Saturday, August 21, 2010

Filters • WordPress passes data to your code • Your code optionally changes the data, then returns it to WordPress Saturday, August 21, 2010

Filters Saturday, August 21, 2010

How to organize your plugin Saturday, August 21, 2010

Saturday, August 21, 2010

Preﬁx cws_spn_function_name() Saturday, August 21, 2010

Singleton Saturday, August 21, 2010

Singleton variation Saturday, August 21, 2010

Most Important Action in WordPress init Saturday, August 21, 2010

Let’s build a plugin! • Insert mailing address and phone number into a post or a page • Use a shortcode... [address] • Conﬁgurable address and phone number • Option to show phone number by default (or not) • Ability to override the phone number default Saturday, August 21, 2010

Settings form handle Setting name Saturday, August 21, 2010

Section handle Title Content callback Settings form handle Saturday, August 21, 2010

HTML id Title Content callback Settings form handle Section handle Saturday, August 21, 2010

http://txfx.net/s/3q Saturday, August 21, 2010

Writing Your First WordPress Plugin

by Mark Jaquith

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