Marko Heijnen discussed several ways to extend WordPress, including hooks, drop-ins, pluggable functions, and pluggable classes. He demonstrated wpcentral.io, which collects WordPress usage data, and opensesh.org, a conference platform built with Node.js. He explained how to build extensions for the future by future-proofing code and looking at new technologies like Node.js.

1. EXTENDING
WORDPRESS AS
A PRO
Marko Heijnen
WordSesh December 2014

2. MARKO HEIJNEN
• Founder of CodeKitchen
• Working for 1&1
• Lead developer of GlotPress
• Core contributor for WordPress
• Plugin developer
• Organizer for WordCamp Belgrade
http://2015.belgrade.wordcamp.org/
WORDPRESS DEVELOPER
The Netherlands

3. TODAY’S
TOPICS
• Current ways to extend WordPress
• Expect the unexpectable
• Demo wpcentral.io
• Build for the future
• Look at new technologies
• Demo opensesh.org
• Questions

4. EXTENDING
WORDPRESS

5. HOOKS
• Hooks are a way for one piece of code to interact
with and modify another piece of code. They make
up the foundation for how plugins and themes
interact with WordPress Core, but they’re also
used extensively by Core itself
• Two types of hooks: Actions and Filters

6. DROP-INS
Single site
• advanced-cache.php
• object-cache.php
• db.php
• db-error.php
• install.php
• maintenance.php
Multisite
• sunrise.php
• blog-deleted.php
• blog-inactive.php
• blog-suspended.php

7. PLUGGABLE FUNCTIONS
• These functions let you override certain core
functions via plugins
• Pluggable functions are no longer being added to
WordPress core
• All new functions instead use filters on their output
to allow for similar overriding of their functionality
• See http://codex.wordpress.org/Pluggable_Functions

8. PLUGGABLE CLASSES
• Using a filter to replace the class that should be
loaded like session_token_manager
• Be able to add your class to be loaded like
wp_image_editors filter

9. EXPECT THE
UNEXPECTABLE
Check out: http://wpcentral.io/

10. WP CENTRAL
WHAT IS IT?
• Showing download history
• Showing version usage history
• List all locales and their current state
• Showing contributors data (currently API only)
• Collects history of locale progress

11. 11

12. 12

13. 13

14. 14

15. WP CENTRAL
HOW IT WORKS
• A lot of data handling by wp_remote_get
• Scrapping profiles.WordPress.org to read data
• Bugs
• Storing 0 values
• Storing invalid data after failed wp_remote_get
requests
• Not checking HTML output from
DOMDocument / DomXPath

16. WP CENTRAL
CACHING STRATEGY
• Expensive query result caching
• Cron job to retrieve download counts and version
usage
• 24 hour cache per locale on request with a max of
5 locales per time
• Using WP CLI to run it command line
• Creating contributor data on request of the API

17. BUILD FOR
THE FUTURE

18. BUILD FOR THE FUTURE
• When writing code, keep the changes you want to
make in mind
• Future proofing is making sure you can easily add
code/features without breaking existing
functionality
• Make the code robust against unexpected problem
situations allowing for graceful recovery or fail-fast,
but do not write code for possible future uses.

19. LOOK AT NEW
TECHNOLOGIES
http://opensesh.org

20. 20

21. NODE.JS
NODEJS.ORG
• JavaScript platform
• Uses an event-driven, non-blocking I/O model
• Lightweight and efficient
• Ideal for real time application
• Lot’s of modules you can use
• Manage with NPM - https://www.npmjs.org

22. OPENSESH

23. OPENSESH.ORG
• A platform for conferences like WordSesh
• Community driven project for the open source community
• Node.js lets you push new sessions
• This with the help of Socket.IO
• When the session is over, you can simply replace it
• Be able to use YouTube files as wait music
• Possible other ideas:
• Create a hangout through WordPress
• Have a personal schedule

24. THE SITE

25. MANAGING CHANNELS

26. BREAK TIME

27. CONNECTING TO WORDPRESS
• Node.js checks cookie data to indicate if user is logged in
• Validates over JSON API and retrieve more user data
• Returns a WP_User object
• Has basic capability check support

28. BASIC CONFIGURATION
var config = {}, channels = [], clients = [];
config.port = 9000;
config.application_host = ‘http://opensesh.com’;
config.application_port = 80;
var app = require('http').createServer(handler),
io = require('socket.io').listen(app),
wordpress = require("wordpress-utils");
app.listen(config.port);
wordpress.set_siteurl( config.application_host );

29. SERVER HANDLER (PART 1)
function handler(req, res) {
if (req.url == "/status") {
res.writeHead( 200 );
res.end();
return;
}
var wp_user = wordpress.connect( req.headers.cookie, req.headers['x-token'] );
if ( wp_user ) { // More code to come }
res.end();
}

30. SOCKET CONNECTION
io.on('connection', function (socket) {
clients[socket.id] = socket;
socket.wp_user = wordpress.connect( socket.handshake.headers.cookie,
socket.handshake.query.token );
socket.on('disconnect', function() {
delete clients[socket.id]
});
var channel_id = parseInt(socket.handshake.query.channel);
socket.emit('publish', { channel : channel_id, url :channels[ channel_id ].url });
});

31. SERVER HANDLER (PART 2)
wp_user.on('wp_connected', function ( data ) {
if ( ! wp_user.can('manage_options') ) {
res.writeHead(403); res.end(); return;
}
var fullBody = ‘';
req.on('data', function(chunk) {
fullBody += chunk.toString();
});
req.on('end', function() { // Access to JSON data }
}

32. SERVER HANDLER (PART 3)
if (req.url == "/publish") {
var json = JSON.parse(fullBody);
if ( json.channel && json.url ) {
if ( ! channels[ json.channel ] ) {
channels[ json.channel ] = {};
}
channels[ json.channel ].url = json.url;
io.sockets.emit( 'publish', { channel : json.channel, url : json.url } );
}
else { res.writeHead(404); }
res.end();
}

33. SERVER HANDLER (PART 4)
else if (req.url == "/channels") {
res.writeHead( 200, {'Content-Type': ‘application/json’} );
res.end( JSON.stringify(channels) );
}
res.end();

34. THANK YOU FOR
LISTENING
QUESTIONS?
@markoheijnen - markoheijnen.com