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


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


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


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


Plugin Header

“Plugin Name” is required.


Basic Structure

• Build some stuff
• Tell WordPress to use that stuff
when WordPress does certain
stuff


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


Actions


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


Filters


How to organize
your plugin


Preﬁx
cws_spn_function_name()


Singleton


Singleton variation


Most Important
Action in WordPress

init

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


Settings form handle

Setting name


Section
handle
Title
Content
callback

Settings
form handle


HTML id

Title
Content
callback
Settings
form handle

Section handle


http://txfx.net/s/3q


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