WP API, what is it good for?
Absolutely Everything!
WordCamp Raleigh - 25 September 2016

Introductions
Evan Mullins
Lead Web Developer
Brown Bag Marketing
@circlecube
circlecube.com
WordPress user since 2006
Full-time web developer since 2007

Currently Version 2.0-beta13.1 (as of 2016.09.24)

API
An application programming interface (API) is a set of
subroutine definitions, protocols, and tools for building software and applications. A
good API makes it easier to develop a program by providing all the building blocks,
which are then put together by the programmer.

REST
REpresentational State Transfer
It describes how one system can communicate state with another. One example would
be the state of a product (its name, description etc) represented as JSON. The
generalised idea of state is termed a resource.

JSON
JavaScript Object Notation is a lightweight data-interchange format.
It is easy for humans to read and write. It is easy for machines to parse and generate. It
is a text format that is completely language independent but uses conventions that are
familiar to programmers. These properties make JSON an ideal data-interchange
language.
JSON is built on two structures:
● A collection of name/value pairs. (object).
● An ordered list of values. (array).

WP REST API

A little history
Ryan McCue started development on an API, and then proposed a WordPress JSON
REST API Project for GSOC in April 2013 (when WordPress was on version 3.5).
The current version 2.0 of the plugin is in beta state and is already partially included
(the infrastructure) in the WordPress core in version 4.4 (December 2015).

A little history
The rest of the REST API is slated for
inclusion in version 4.7 after considerable
discussion and planning (it was originally
intended for 4.5). It was delayed in order to
build it out with more endpoints.
Until merging this API into core
(hopefully in 4.7 - December 2016-ish),
we’ll need to install the REST API feature
Plugin.

Resources
Github
https://github.com/WP-API/WP-API
Documentation
http://v2.wp-api.org/
WP Plugin -
https://wordpress.org/plugins/rest-api/

#core-restapi
Slack Channel

Nutshell
So in a nutshell, rather than getting your content or data via a
webpage as part of a website with php, html, css and javascript,
you can use whatever you want and retrieve your data via the
API. You’ll get json data that is compact and fast to transfer and
then you can do endless things with it. Create an app, load it into
another website, analyze it as data… it’s a great step for
WordPress and a great step to continuing democratizing the web.

Tools
Postman -
HTTP or
API client
Also: REST Easy for Firefox or httpie for the command line

Back to WordPress
The plugin/API exposes your data in JSON format in the following content types:
Posts
Pages
Media
Custom Post Types
Post Meta
Revisions
Comments
Terms
Users

Routes / Endpoints
Endpoints are functions available through the API and are simply urls. This can be
things like retrieving the API index, updating a post, or deleting a comment. Endpoints
perform a specific function, taking some number of parameters and return data to the
client.
A route is the “name” you use to access endpoints, used in the URL. A route can have
multiple endpoints associated with it, and which is used depends on the HTTP verb.

Routes / Endpoints Example
With the URL http://example.com/wp-json/wp/v2/posts/123
The “route” is wp/v2/posts/123 - The route doesn’t include wp-json because
wp-json is the base path for the API itself.
This route has 3 endpoints:
● GET triggers a get_item method, returning the post data to the client.
● PUT triggers an update_item method, taking the data to update, and returning the
updated post data.
● DELETE triggers a delete_item method, returning the now-deleted post data to the
client.

GET /wp/v2/posts get list of latest posts
GET /wp/v2/posts/<id> retrieve a single post
V1: https://2016.raleigh.wordcamp.org/wp-json/posts
V2: http://demo.wp-api.org/wp-json/wp/v2/posts
V2: http://demo.wp-api.org/wp-json/wp/v2/posts/470
GET - to read data

https://2016.raleigh.wordcamp.org/wp-json/posts/ (Old API)

http://demo.wp-api.org/wp-json/wp/v2/posts/470

Standard arguments as you’d expect and more
One Example:
filter Use WP Query arguments to modify the response;
private query vars require appropriate authorization.
GET

https://app.circlecube.com/uspresidents/wp-json/wp/v2/president?filter[posts_per_page
]=-1&filter[order]=DESC&filter[orderby]=meta_value_num&filter[meta_key]=took_office

PUT - to create or update data
POST /wp/v2/posts create post
POST /wp/v2/posts/<id> update existing post

DELETE - to trash
DELETE /wp/v2/posts/<id>

Authentication

Authentication
If you are building a theme or a plugin and want to access
the API of the site you’re on you’ll want to authenticate
with a cookie. WordPress already does this, so you’ll just
want to check if the user has permissions to do what
you’re attempting to do.
Use a nonce (WordPress security token) to connect to a
local API if your theme or plugin wants to connect to the
API of the site it’s on via ajax.

Authentication
Write a nonce in a
wp_localize_script
with wp_create_nonce
and then pass that nonce
value in your header.

Authentication
Write a nonce in a
wp_localize_script
with
wp_create_nonce
and then pass that
nonce value in your
header.

Authentication
OAuth authentication is the main authentication handler used for external clients. It
requires installing the OAuth plugin on the site which then handles authorizations and
tokens.
For examples on how to use OAuth Authentication checkout the Demo PHP API
Client, the CLI client or the API console.

Extend - Do More
Modifying Responses
Adding Endpoints
Custom Content Types
$args = array( 'show_in_rest' => true );

Examples

US Presidential Mobile App
An app will test your knowledge and teach you the Presidents of the USA – powered
with WordPress via
the REST API.

US Presidential Mobile App

https://app.circlecube.com/uspresidents/wp-json/wp/v2/president?filter[posts_per_page
]=-1&filter[order]=DESC&filter[orderby]=meta_value_num&filter[meta_key]=took_office

USMNT Soccer App
A similar app powered by the WordPress REST API, but with data centering around
the US Soccer team.

Sitemapper
An in-house plugin at Brown Bag
Marketing to quickly get up and
running with a new WordPress site in
our prototyping and wireframing
multisite.
Construct your sitemap and the plugin
will create a new site (in the multisite
network) and via the API create new
pages according to the supplied
sitemap.

Digital Dashboard
Angular web app built at
Brown Bag Marketing to
display live stats about a
bunch of sites. Connects
to sites like pingdom,
analytics etc, . The sites
are stored in WordPress
as a CPT and loaded
dynamically and it has
featured content that’s
pulled from the WP API.

Questions, Comments, More (better) Examples, Discuss
?

Additional Reading
http://v2.wp-api.org/reference/posts/
https://demo.wp-api.org/
https://deliciousbrains.com/creating-mobile-app-wp-api-react-native/
https://css-tricks.com/wp-rest-api-remote-control-wordpress/
https://code.tutsplus.com/tutorials/introducing-the-wp-rest-api--cms-24533
https://www.sitepoint.com/wp-api/
https://webdevstudios.com/2016/01/05/an-overview-of-the-wordpress-json-api-version-2/
https://www.wpkube.com/implementations-wp-rest-api/

Thank You
!
Slides and code available at https://circlecube.com/does-wordpress/