WordPress currently powers over 1/5th of the internet and is growing. Historically, people think of WordPress as a blogging platform or use it as a CMS, but can this tool known and used by millions of people also be used to create complex applications? WordPress is familiar, easy to use, actively developed and supported, and has a powerful codebase that allows one to quickly develop applications and websites. These things make WordPress a great option to develop you next application. We will walk through examples of WordPress's use to create applications and very complex sites and then dive into the internals of WordPress that make this happen including: Custom Data Types, WordPress Hooks, Database Interactions, Connecting to Remote APIs, The WordPress JSON API, Caching, Extensibility, User and Role Management, Templates, and URL Rewriting.

1. WordPress
as an
Application
Framework
Dustin Filippini
Developer @ WebDevStudios
@dustyf
dustyf.com

5. WWhat Makes a Framework Good?
• Easy
• Well Supported
• Extensible

6. EASY
It does work
for you

7. Well
Supported
We are here to help!

8. Extensible
Add on More Dogs

9. A Real World Example
Create a billing/invoicing system using WordPress!
Think… FreshBooks

10. “I need an easy,
reusable way to
store, access,
and categorize
structured data”
Custom Post Types &
Custom Taxonomies.
function register_invoice() {
$args = array(
'public' => true,
'label' => 'Invoices'
);
register_post_type( 'invoice',$args );
}
add_action(‘init','register_invoice');
function create_invoice_status() {
register_taxonomy(
'status',
'invoice',
array(
'label' => ‘Invoice Status',
'rewrite' => array( 'slug' =>
‘invoice_status' ),
'hierarchical' => false,
)
);
}
add_action( 'init',
‘create_invoice_status' );

11. “I need to store
data related to
my structured
data and users.”
Post Meta and User Meta.
update_post_meta( $post_id,
‘purchase_order_number’, $value );
update_user_meta( $user_id, ‘job_title’,
$value );

12. “I need users to
be able to access
data and limit
access to
different users”
Create users and assign
roles and capabilities to
access different parts of
your application.
Built-in User Management panel and
ability to manipulate through your code.
ADD A NEW ROLE
add_role(
‘client',
‘Client',
array(
'read' => true,
'edit_posts' => true,
)
);
ADD A CAPABILITY TO THE ROLE
$role = get_role( ‘client' );
$role->add_cap( ‘view_invoices’ );
RESTRICT ACTION
if ( current_user_can( ‘view_invoices’ )
{
// Do Something
}

13. “I need to create
custom views
for different
types of data"
Templating through
WordPress Theme API.
Allows you to define different
templates for different types
of content and views.
BASIC WORDPRESS PAGE LOOP
get_header();
if (have_posts()) :
while (have_posts()) :
the_post();
the_content();
endwhile;
endif;
get_sidebar();
get_footer();
TEMPLATE FILE NAMING
single-invoices.php - Single Invoice
View
archive-invoices.php - Archive of
Invoices
LOADING CUSTOM TEMPLATES
get_template_part( 'loop', 'index' );
will do a PHP require() for the first
file that exists among these, in this
priority:
wp-content/themes/themename/loop-
index.php
wp-content/themes/themename/loop.php

14. “I need to
customize
default actions
of my app”
WordPress has hooks for nearly
everything that happens.
Use ‘add_action’ to do execute
custom code at a certain time.
Use ‘add_filter’ to change
default values.
function email_invoice( $post_id ) {
$to = ‘dusty@dustyf.com’;
$subject = get_the_title( $post_id );
$message =
get_the_permalink( $post_id );
wp_mail( $to, $subject, $message );
}
add_action(‘save_post’,‘email_invoice’);
function mod_title( $title, $post_id ) {
if (
‘invoice’ == get_post_type($post_id) &&
has_term( ‘paid’,
‘invoice_status’, $post_id
) {
$title = ‘PAID: ‘ . $title;
}
return $title;
}
add_filter( ‘the title’, ‘mod_title’,
10, 2 );

15. “I need easy,
secure, access
to the
database”
The wpdb class provides
easy, secure database
interaction for those times
you need it.
global $wpdb;
$results = $wpdb->get_results( 'SELECT *
FROM wp_options WHERE option_id = 1');
$wpdb->insert(
‘payments_made',
array(
'client' => 'Apple',
‘invoice_num' => 123
),
array(
'%s',
'%d'
)
);
// PROTECT FROM SQL INJECTION
$metakey = ‘purchase_order_num’;
$metavalue = ‘12345’;
$wpdb->query( $wpdb->prepare(
"INSERT INTO $wpdb->postmeta
( post_id, meta_key, meta_value )
VALUES ( %d, %s, %s )",
10,
$metakey,
$metavalue
) );

16. “I need to have
a reliable way
to rewrite
URLs”
WordPress rewrites posts,
pages, taxonomies, and
custom post types by
default. But, you can use
the Rewrite API to make
custom rules.
function custom_rewrite() {
add_rewrite_rule('^invoice/
([0-9]+)/?',
'index.php?page_id=$matches[1]',
'top');
}
add_action(‘init','custom_rewrite');
Now, you can access the same page as
http://example.com/invoice/95

17. “Different app
instances for
different users/
clients/
companies.”
WordPress multisite allows
you to create multiple site/
app instances. Each can
share or have different
functionality, views, settings,
userbases, and more.
Add the following to your wp-config.php
and follow the instructions in wp-admin
under Settings > Network Setup
define( 'WP_ALLOW_MULTISITE', true );
Use Case: Each company using this
invoice system can have their own
instance at their own url…
google.example.com or example.com/google

18. “I need to be
able to connect
with third-party
services”
Built in HTTP API supports
multiple transport methods
for your HTTP requests
because different hosting
environments support
different things.
$response = wp_remote_post( $url, array(
'method' => 'POST',
'timeout' => 45,
'redirection' => 5,
'httpversion' => '1.0',
'blocking' => true,
'headers' => array(),
'body' => array( 'username' =>
'bob', 'password' => '1234xyz' ),
'cookies' => array()
)
);
$response returns a nice array
AlSO:
wp_remote_request()
wp_remote_get()
wp_remote_post()
wp_remote_head()
wp_remote_retrieve_body()
wp_remote_retrieve_header()
wp_remote_retrieve_headers()
wp_remote_retrieve_response_code()
wp_remote_retrieve_response_message()

19. “I need to
improve
performance by
limiting requests”
Transients allow you quickly
store data with an expiration
for quick access.
Get more in depth with
caching plugins.
set_transient(
‘special_query’,
$special_query,
60*60*12
);
get_transient( 'special_query' );
//EXAMPLE
if ( false === ( $special_query =
get_transient( 'special_query' ) ) ) {
$special_query_results = new WP_Query(
'cat=5&order=random&tag=tech&post_met
a_key=thumbnail'
);
set_transient(
'special_query',
$special_query,
4 * HOUR_IN_SECONDS
);
}
- get_transient
- set_transient
- wp_cache_set
- wp_cache_get

20. “I need to be
able to open
my application
to third parties”
Create an API for your app
using the XML-RPC API or
the new JSON REST API
JSON REST API will be in WP Core soon,
but is now available in a stable plugin.
Out of the box provides:
• Endpoints for retrieving, creating,
editing, and deleting all built-in post
types and registered custom post types
• Also, media, users, taxonomies and meta
• Can be extended to support your other
types of data

21. “I don’t want to
create things that
have been done
hundreds of times
before”
Thousands of WordPress
Plugins both free and
premium. Also, feel free to
use other PHP Libraries.
35,000+ Free Plugins at wordpress.org/
plugins/ and many great premium plugins.
BuddyPress - Social Network
BBPress - Forums
BadgeOS - Award Achievements
CMB2 - Custom Fields and Metaboxes
Gravity Forms - Form Building
Posts 2 Posts - Relational post linking
WooCommerce - eCommerce
Events Calendar Pro - Calendar
Or build your own to use over and over
(or to share or sell!)

22. MOAR
EXAMPLES
WordPress is being used as
an application framework all
over the web.
Reactor by AppPresser
(http://reactor.apppresser.com/)
WP Powered application that builds
mobile applications from your WP site.
DesktopServer 4.0
(http://serverpress.com/)
Desktop application to create local
development sites.
ManageWP
(http://managewp.com/)
Upgrade, perform backups, monitor, track
statistics, and manage multiple WP
sites.
YMCA Y-MVP App
(http://www.ymcanyc.org/association/
pages/y-mvp)
iPad application used as a kiosk at YMCA
to allow members to scan card and log
exercise activities.
Frito-Lay Project Management
(http://liftux.com/portfolio/frito-lay-
creative-project-management-app/)
Custom project management app.

23. Easy

24. Well
Supported

25. Extensible

26. Go Forth
& Create Apps
Dustin Filippini
dusty@dustyf.com
@dustyf
dustyf.com
webdevstudios.com