This is an introduction for those who want to start developing plugins for Wordpress blog engine

2. The first steps…
• Pre‐development issues
– Wordpress Plugin Directory
– Plugin and File Names
– File Headers
• Wordpress Plugin Hooks
– Actions
– Filters
• Adding data to wordpress database
– Creating tables with plugins
• Adding Administration Menus
– Creating options page
• “Hello Dolly” example
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3. Pre‐development issues (1)
Wordpress Plugin Directory
code
javascript
wp‐content plugins your plugin
css
place your plugin here images
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4. Pre‐development issues (2)
Plugin and File Names
Choose your plugin’s name carefully. Think about
what the plugin will do, and make a, hopefully unique,
name for it.
It is good for the names of your php files to be derived
from your chosen plugin name.
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5. Pre‐development issues (3)
File Headers
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6. Wordpress Plugin Hooks (1)
Hooks are provided to allow your plugin to 'hook into' the rest
of WordPress; that is, to call functions in your plugin at specific
times, and thereby set your plugin in motion.
Hooks
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7. Wordpress Plugin Hooks (2)
Hooks = Actions + Filters
Actions are triggered by specific events (e.g. publishing a
post ) that take place in WordPress. Your plugin can respond
to the event by executing a PHP function
Action Event
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8. Wordpress Plugin Hooks (3)
Hooks = Actions + Filters
Filters - Functions
DATA
Filters are functions that WordPress passes data through
at certain points in execution, just before taking some
action with the data such as adding it to the database or
sending it to the browser screen.
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9. Adding data to Wordpress database
Create tables with plugins
There are two types of information you could store
• Setup Information: user choices that are entered when the user first sets up
your plugin.
• Data: information that is added as the user continues to use your plugin
Steps…
1. Write a PHP function that creates the table.
2. Ensure that WordPress calls the function when the plugin is activated.
3. Create an upgrade function, if a new version of your plugin needs to have a
different table structure.
http://codex.wordpress.org/Creating_Tables_with_Plugins#Create_Database_Tables
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10. A simple example
$table_name = $wpdb->prefix . quot;liveshoutboxquot;;
// check if there is a table with the same name
if($wpdb->get_var(quot;show tables like '$table_name'quot;) != $table_name) {
// SQL Statement
$sql = quot;CREATE TABLE quot; . $table_name . quot; (
id mediumint(9) NOT NULL AUTO_INCREMENT,
time bigint(11) DEFAULT '0' NOT NULL,
name tinytext NOT NULL,
text text NOT NULL,
url VARCHAR(55) NOT NULL,
UNIQUE KEY id (id)
);quot;;
// Creating the table
require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
dbDelta($sql);

11. A simple example
$welcome_name = quot;Mr. Wordpressquot;;
$welcome_text = quot;Congratulations, you just completed the installation!quot;;
// SQL Statememt
$insert = quot;INSERT INTO quot; . $table_name .
quot; (time, name, text) quot; .
quot;VALUES ('quot; . time() . quot;','quot; . $wpdb->escape($welcome_name) . quot;','quot; . $wpdb->escape($welcome_text) .
quot;')quot;;
// Adding Data into the table
$results = $wpdb->query( $insert );

12. Adding Administration Menus
Create options page
Top-level menus: Settings, Manage, Plugins, Presentation, Write, Users
Admin Menu Functions
• add_menu_page: create a top-level menu
• add_submenu_page: define one or more sub-menu pages
In the above wordpress functions the developers defined the name of their php
functions which are responsible to build the options pages.
See an example here
http://codex.wordpress.org/Creating_Options_Pages
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13. Hello Dolly example
Hello Dolly Lyrics Chose randomly one lyric and place it
the upper right of your Administation
panels
add_action('admin_footer', 'hello_dolly');
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14. Wordpress Development Community
Are you ready to enter into an
evolving development community?
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15. Matt Mullenweg
Creator of Wordpress.org
14th place
The 25 most influential
people on the web
(2008)
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16. More details on the internet…
The truth is out there…
http://codex.wordpress.org/Writing_a_Plugin#WordPress_Plugin_Hooks
http://codex.wordpress.org/Plugin_API
http://codex.wordpress.org/Creating_Tables_with_Plugins
http://codex.wordpress.org/Adding_Administration_Menus
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17. THE END
Thank you!
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