WordPress Plugin Development

Presented ByThirupathi.J

Concepts

What is wordpress?

How to install wordpress?

What is wordpress plugin?

What do you need to make a wordpress plugin?

Plugin Structure?

Plugin API?

What is WordPress?

WordPress is an open source blog publishing application powered by PHP and MySQL which can also be used for content management. It has many features including a workflow, a plugin architecture and a templating system.

How to install WordPress?

Download the wordpress latest version from:

http://wordpress.org/download/

What is a WordPress plugin?

Little applications used to enhance functionality or add specific functions tailored to a site's specific needs.

Some plugins:

Capitalize Titles of Pages and Posts WordPress Database Backup WordPress.com StatsComment Hilite

What do you need to make a plugin?

a problem to solvesome PHP knowledge

some spare timea test server with your test wordpress (XAMPP is good.)

Plugin Directory Structure

Your Plugin:/wp-content/plugins/my-plugin

Inside “my-plugin”readme.txtscreenshot-1.pngmy-plugin.php

Always put it in a directory!

Uses 'dashes' and not 'underscores'http://codex.wordpress.org/Writing_a_Plugin#Names.2C_Files.2C_and_Locations

Plugin API

- Enabled "hooks"

- Extend functionality withoutediting the core code

- Two categories:Actions and Filters

2 Kinds of WordPress Hooks

Actions = “Do Something”

Filters = “Transform”

ActionsActions are the hooks that the WordPress core launches at specific points during execution, or when specific events occur. Your plugin can specify that one or more of its PHP functions are executed at these points, using the Action API.

add_action( 'hook_name', 'your_function_name', [priority], [accepted_args] );

Filters

Functions that modify text, lists andvarious types of information that areused and produced by WordPress.

add_filter('hook_name', 'your_filter_function', [priority], [accepted_args]);

Writing Your First Plugin

readme.txt

• http://codex.wordpress.org/Writing_a_Plugin#Readme_File

• http://wordpress.org/extend/plugins/about/readme.txt

Useful only for publishing toWordPress Plugin Directory

Information about your plugin:Description, Installation, Changelog, Donation

Links, Tags, etc...

screenshot-1.png

•Useful only for publishing to•WordPress Plugin Directory

my-plugin.php

4 parts to a pluginPlugin HeaderHooksPHP CodeTemplate Code

File Structure

Plugin Headers

http://codex.wordpress.org/Writing_a_Plugin#Standard_Plugin_Information

Plugin Headers

http://codex.wordpress.org/Writing_a_Plugin#Standard_Plugin_Information

Always on top, no choice

Fill in with your own details

Hooks (Filters)

Hooks (Filters)

After plugin headers (my preferance)

Makes it easier to find

PHP Code

Plugin 1

Figure out what you want to do.

I want to convert all instances of “WordPress” to “WORDPRESS”in a post's content.

the_content (filter)

http://codex.wordpress.org/Plugin_API/Filter_Reference/the_content

add_filter

http://codex.wordpress.org/Plugin_API/Filter_Reference/the_content

add_filter

http://codex.wordpress.org/Plugin_API#Hook_to_WordPress

②

① Hook Name

② Callback

①

Hook Callback

Determines what PHP function to call

Callback can be either:String; orArray of 2 strings (my preference)

Hook Callback

StringCalls a function

Array of 2 stringsCalls a static function in a class

They do the same thing

I Prefer Array Callbacks

Allows me to segment my code

Lower chances of name conflicts

Easily tell which function belongs to which hook

Filters are Transformations

filters have to return a transformation

Filter return Values

A filters return value, is the result of the transformation

②① return

② transformation

①

http://php.net/manual/en/function.preg-replace.php

Plugin 2

Figure out what you want to do.

I want to BOLD all instances of “WORDPRESS”

in a post's content.

Hook Priority

http://codex.wordpress.org/Plugin_API#Hook_to_WordPress

Priority

②

② Callback

① ③②②

③ Priority (optional)

① Hook Name

http://codex.wordpress.org/Plugin_API#Hook_to_WordPress

Which one goes first?

WordPress2WORDPRESS#the_content

ABolderWordPress#the_content

Default Priority

10smaller numbers = higher prioritylarger numbers = lower priority

http://codex.wordpress.org/Plugin_API#Hook_to_WordPress

Therefore

Order of execution:

(10) WordPress2WORDPRESS#the_content(20) ABolderWordPress#the_content

THANK YOU