This document provides an introduction to developing WordPress plugins. It discusses what plugins are, popular existing plugins, and steps for creating a photo slider plugin from scratch. These steps include creating plugin files, using hooks for activation/deactivation, actions and filters, including styles and scripts, assigning content via shortcodes, and next steps like template tags and internationalization. Resources for further plugin development learning are also provided.

1. Developing WordPress
Plugins : For Beginners
M A Hossain Tonu
http://mahtonu.wordpress.com

2. Who am i ?
• Tech Blogger http://mahtonu.wordpress.com
• Hacker, Community activist, FOSS advocate
• Works atVantage Labs Dhaka
• @mahtonu
• Authored the title “PHP Application
Development with NetBeans: Beginner's
Guide” http://link.packtpub.com/6HaElo

3. Inside scoop!
• What is Plugin?
• Popular Plugins
• Creating a Plugin from Scratch
• Sanity Practices and a Plugin foundation
• Activation, Deactivation Hooks
• Hooks: Actions and Filters
• Shortcodes
• Resources for Plugin Developer

4. WordPress Plugins allow easy modification,
customization, and enhancement to a
WordPress website.

5. Instead of changing the core programming
of WordPress, you can add functionality
with WordPress Plugins.

6. Book’s Definition
A WordPress Plugin is a program, or a set of
one or more functions, written in the PHP
scripting language, that adds a specific set of
features or services to the WordPress
weblog, which can be seamlessly integrated
with the weblog using access points and
methods provided by the WordPress Plugin
Application Program Interface (API).

7. Popular WP Plugins
http://wordpress.org/plugins/browse/popular/

8. Popular WP Plugins

9. Popular WP Plugins

10. Popular WP Plugins

11. Popular WP Plugins

12. Popular WP Plugins

13. Popular WP Plugins

14. Popular WP Plugins

15. Popular WP Plugins

16. Popular WP Plugins

17. There are huge number of
Plugins out there waiting for you

18. Plugins Repo Today!
25,276 plugins, 464,157,564 downloads, and
counting

19. Lets Create A Plugin
from Scratch...

20. How about a Photo
Slider?

21. Prerequisites?
• HTML/CSS
• PHP
• JavaScript / JQuery
• MySQL

22. Prerequisites? designer?
• HTML/CSS
• PHP
• JavaScript / JQuery
• MySQL

23. Frond-end of the Slider Plugin

24. Plugins Directory

25. Dashboard | Plugins

26. Things to remember
• A unique descriptive name
• Naming: my-plugin.php or /my-plugin/ folder
• Readme.txt format for wordpress.org/
extend/plugins
• Plugin home page
• File headers (very important!)

27. Creating Plugin File
A single PHP file
my-slider/my-slider.php
inside your plugin folder

28. Creating Plugin File
<?php
/*
Plugin Name: My Slider
Plugin URI: http://mahtonu.wordpress.com/
Description: Slider Plugin for WordPress
Version: 1.0
Author: M A Hossain Tonu
Author URI: http://mahtonu.wordpress.com/
License: GPLv2 or later
*/
?>

29. Creating Plugin File

30. Parameters
• Plugin URI – is used to let users know about the details of the plugin and
available download options.This isn’t mandatory and you can keep it blank, if
you don’t have an intention of making the plugin publicly available.
• Description – is used to provide a summary of functionality of the plugin.
• Version – is used to define the version and you can use any numbering
format as you wish. Plugins need be upgraded with each WordPress version
upgrade.Therefore it’s good to have proper version numbering even though
it’s not mandatory.
• Author and Author URI – is used to provide details about the
developer of the plugin.
• License – is used to define the conditions for using this plugin.We can
include standard licence such as GPL2 or just mention something we prefer
such as Free to use.

31. Plugin Api
• Enabled “hooks”
• Extend functionality without editing the
core code
• Two categories:Actions and Filters

32. WordPress Plugin Activation
and Deactivation Hooks
register_activation_hook()
register_deactivation_hook()

33. WordPress Plugin Activation
and Deactivation Hooks
function my_slider_activation() {
}
register_activation_hook(__FILE__,
'my_slider_activation');
function my_slider_deactivation() {
}
register_deactivation_hook(__FILE__,
'my_slider_deactivation');

34. Why Do We Use Activation/
Deactivation Hooks
• Create custom database tables on
activation to store data and remove tables
on deactivation.
• Create custom options for plugins and
activation and reset in deactivation.
• Validate other dependent plugin on
activation.
• Any other necessary task you need to
execute in activation.

35. Actions
Specific points in the WordPress code that
can be used to trigger plugin-specified events
and functions
add_action( 'hook_name', 'your_function_name',
[priority], [accepted_args] );

36. Sample action: “wp_login”
function notify_on_login() {
// your code here
// email to admin, etc...
}
add_action('wp_login', 'notify_on_login');

37. Filters
Functions that modify text, lists and various
types of information that are used and
produced by WordPress
add_filter('hook_name', 'your_filter_function',
[priority], [accepted_args]);

38. Sample filter: “the_content”
function add_rss_invite() {
// output to screen the link to RSS feed
// if 1st time visitor
}
add_filter('the_content', 'add_rss_invite');

39. Understanding the
Components of Slider
• jQuery library
• jQuery plugin file
• Initialization code
• CSS files used for plugin
• HTML or Images used for sliding

40. My Slider Directory Structure

41. Sample HTML
<html>
<head>
<script type='text/javascript' src='http://code.jquery.com/
jquery-latest.min.js'></script>
<script type='text/javascript' src='jquery.slides.min.js'></
script>
<script type='text/javascript'>
jQuery(function() {
jQuery('#slides').slidesjs({
width: 940,
height: 528,
navigation: false
});
});
</script>
</head>
<body>
</body>
</html>

42. Including Scripts : my-slider.php
<?php
add_action('wp_enqueue_scripts', 'my_scripts');
function my_scripts() {
wp_enqueue_script('jquery');
wp_register_script('slidesjs_core', plugins_url('js/
jquery.slides.min.js', __FILE__), array("jquery"));
wp_enqueue_script('slidesjs_core');
wp_register_script('slidesjs_init', plugins_url('js/
slidesjs.initialize.js', __FILE__));
wp_enqueue_script('slidesjs_init');
}
?>

43. Including Scripts : my-slider.php
• wp_enqueue_script is used to include the script file to the
HTML document
• wp_register_script is used to register a script file into
WordPress
• plugins_url function will provide the URL of the plugin
folder.
• SlidesJs core plugin file is named as jquery.slides.min.js
• The initialization part of the library inside
slidesjs.initialize.js jQuery(function() {
jQuery('#slides').slidesjs({
width: 940,
height: 528,
navigation: false
});
});

44. Including Styles : my-slider.php
add_action('wp_enqueue_scripts', 'my_styles');
function my_styles() {
wp_register_style('slidesjs_example', plugins_url('css/
example.css', __FILE__));
wp_enqueue_style('slidesjs_example');
wp_register_style('slidesjs_fonts', plugins_url('css/font-
awesome.min.css', __FILE__));
wp_enqueue_style('slidesjs_fonts');
}

45. Assigning Content to Slider
Using Shortcode: my-slider.php
add_shortcode("my_shortcode", "my_shortcode_function");
function my_shortcode_function() {
return "<h1>Hello Shortcodes</h1>";
}

46. Assigning Content to Slider
Using Shortcode

47. Integrating Slider Using
Shortcode: my-slider.php
add_shortcode("my_slider", "my_display_slider");
function my_display_slider() {
$plugins_url = plugins_url();
echo '<div class="container">
<div id="slides">
<img src="'.plugins_url( 'img/example-slide-1.jpg' , __FILE__ ).'" />
<img src="'.plugins_url( 'img/example-slide-2.jpg' , __FILE__ ).'" />
<img src="'.plugins_url( 'img/example-slide-3.jpg' , __FILE__ ).'" />
<img src="'.plugins_url( 'img/example-slide-4.jpg' , __FILE__ ).'" />
<a href="#" class="slidesjs-previous slidesjs-navigation"><i
class="icon-chevron-left icon-large"></i></a>
<a href="#" class="slidesjs-next slidesjs-navigation"><i class="icon-
chevron-right icon-large"></i></a>
</div>
</div>';
}

48. Finally!
shortcode = [my_slider]

49. Take away
• Plugin Creation Basics
• Sample Plugin Created from Scratch
• Best Practices
• Hooks:Activation & Deactivation,
Actions & Filters
• Shortcodes: Usage and Creation

50. What should be my next
Steps?
• Template Tags
• Data Saving, Add/Update Options
• Internationalization
• Submit Plugin to Repository
• Admin:Add to admin menu, Control
settings from Dashboard
• Earn Money!!!

51. Questions?

52. Resources
• Writing a Plugin: http://codex.wordpress.org/Writing_a_Plugin
• Articles and resources for Plugin developers: https://
codex.wordpress.org/Plugin_Resources
• basics about how WordPress Plugins are written: https://
codex.wordpress.org/Plugins#Default_Plugins
• Plugin API http://codex.wordpress.org/Plugin_API
• Plugin API / Action Reference http://codex.wordpress.org/
Plugin_API/Action_Reference
• Plugin API / Filter Reference http://codex.wordpress.org/

53. More Resources
• http://www.slideshare.net/rebelpixel/developing-wordpress-
plugins-presentation
• http://www.slideshare.net/chzigkol/wordpress-plugin-
development-short-tutorial-presentation
• http://www.slideshare.net/gamerz/developing-plugins-for-
wordpress
• http://www.slideshare.net/williamsba/create-your-first-wordpress-
plugin

54. Shameless Promotion
http://link.packtpub.com/6HaElo