We’ve all heard about the WordPress REST API now and then. The API allows us to access site data from other applications as needed. We can access WordPress data (using the existing API endpoints) as well as custom data from plugins etc. by creating custom API endpoints as needed.
Today, we’re going to look into creating a custom route and endpoint. This can essentially be helpful when we want plugin data to be accessed via the REST API. Before we dive in, we’ll first look at some basics concepts.
The WordPress REST API can be accessed at
/wp-json/. We can request access to the WordPress REST API index at
https://mysite.com/wp-json/. It lists basic site details like the site name, access url, timezone and api details like namespaces registered, endpoints available and so on.
Some of the key concepts and terms that will help us get started with the API are as below:
1. Routes & Endpoints
A route, in the context of the WordPress REST API is a URI which can be mapped to different HTTP methods. The mapping of an individual HTTP method to a route is known as an endpoint. So essentially, endpoints are functions available through the API. These functions include things like updating a post, deleting a comment and so on.
wp/v2/posts/123 is a route. Here,
wp/v2 is the namespace (explained in detail later),
posts indicates the type of data that is being retrieved and
123 is the post ID. This route has 3 endpoints
- GET triggers a
get_itemmethod, returning the post data to the client.
- PUT triggers an
update_itemmethod, taking the data to update, and returning the updated data to the client.
- DELETE triggers the
delete_itemmethod, returning the now deleted post data to the client.
One of the primary classes in the WordPress REST API infrastructure is
WP_REST_Request. This class is used to store and retrieve information for the current request. Requests can be submitted remotely via HTTP but may also be made internally from PHP with WordPress.
Responses are the data you get back from the API. The
WP_REST_Response class provides a way to interact with the response data returned by endpoints. Responses can return the desired data, and they can also be used to return errors.
WordPress has routes and endpoints to read, update, delete almost all of it’s data. However, since there are thousands of plugins based on WordPress out there, it is safe to assume that those plugins will have their custom data, which they will need access to using the WordPress REST API.
Rest easy, WordPress allows us to create our own custom routes and endpoints. WordPress provides us with hooks and functions to do the needful. Taking an example, we will write a patch of code to register a new route that allows us to return some simple text.
Creating a custom endpoint
The first argument in the
register_rest_route function is the namespace. This namespace helps us to group together all our routes.
It is extremely important to add namespaces to your routes. The “core” endpoints use the
wp/v2 namespace. The first part of the namespace is
wp, which represents the vendor name; WordPress and v2 is the version number. We’re going to use
my-route as the namespace here.
The second argument is the resource path. The resource path signifies what resource the endpoint is associated with (like posts, comments and so on). In our case, we will name it my-phrase.
The third argument is an array of options. Here we specify what methods the endpoint can use and callback functions for each method. This argument also allows us to provide a permissions callback, which can restrict access for the endpoint to certain users.
Once this endpoint is created, you can access it at the below url
rest_ensure_response is the function that is used to return the data. This function returns a new instance of the
WP_REST_RESPONSE class for the data being returned. This is needed to make sure the data is returned in the correct format. The function also allows for errors to be passed back.
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Restricting access to the endpoint
Restricting access can be achieved by using
permission_callback argument allows us to setup permissions making sure the data is accessed only by users who have authority to access it.
In the example above, I’ve limited the access to only those users that have the
'edit_posts' authority. So if I access the link
https://mysite.com/wp-json/my-route/my-phrase as a guest or a logged in user with authority lower than that of an author, I will see an error message as below:
We will now look at an example to fetch some post data. Although this example simply fetches some data for all the posts on the site, you can write the code to fetch your custom plugin data on similar lines.
Fetching WordPress data using an endpoint
The above code is very similar to what we have done in our first example in this post.
We first registered an endpoint as
my-posts. In the callback function, we fetched all the posts and returned some data from the same.
wp_reset_postdata function ensures that the global
$post is restored to the current post in the main query.
WP_Query, hence it is necessary to ensure we restore the post data.
You can access the results from the above code on
The above is a list of all the posts present on the site irrespective of the author.
Filtering the data
Continuing on the above example, we will now try to fetch posts for a given author only.
We have added a new argument in the third parameter being passed to the
'args' allows us to add as many arguments as we want. Based on the same, the data will be filtered. Note that we’ve also modified the route to ensure that the author ID is an expected parameter.
As you might’ve noticed in the first screenshot of the posts, we have 2 posts each from 2 different authors.
When we access the path
https://mysite.com/wp-json/my-route/my-posts/1 it will display the posts with the author ID 1.
Similarly, when we access the path
https://mysite.com/wp-json/my-route/my-posts/29, it will display the posts from the author ID 29.
Being able to read data from a WordPress site using the REST API is just skimming the surface of the pond. The API allows you to not only read the data, it enables you to filter the data based on the arguments passed, validate that the user has the authority to view the data as well.
Apart from that, you can edit, create and delete data using the API as well.
I hope this post helps you get started with creating your custom API endpoints. To help you move forward with this, the WordPress REST API handbook is located here. In case if you have tried using the same methods or alternate methods with better results, please let us know in the comments below!