Using WordPress as a headless system, is nothing new. You can easily build out your own REST API or use the long available HTTP REST API 1.0+ for WordPress.

But with the new HTTP REST API 2.0+ its getting really easy to build out your own REST API Namespace and assign routes for all your JSON needs.

The new REST API will make its appearance in WordPress 4.4, but you can start now by adding the plugin to your system. When the plugin detects 4.4+ it will only load functionality not already present in the core.

A ROUTE

A route tells the API to respond to a given request with a specific function (endpoint). This adds the permalink structure to WordPress so that your functionality can be accessed via an url like this: http://yourdoman.com/wp-json/yourplugin/v1/myfunction/your_parameter

add_action( 'rest_api_init', function () {
    register_rest_route( 'your_namespace/v1', '/your_endpoint/(?P<your_parameter>\d+)', array(
        'methods' => 'GET',
        'callback' => 'your_endpoint',
    ) );
} );

add_action( 'rest_api_init', function () {

register_rest_route( 'your_namespace/v1', '/your_endpoint/(?P<your_parameter>\d+)', array(

'methods' => 'GET',

'callback' => 'your_endpoint',

) );

} );

THE ENDPOINT

The Endpoint is the callback handled by the route. Each endpoint can have additional parameters attached:

custom permissions
default values
sanitization callback
validation callback
field requirements and more

RETURN VALUE

The return values from the endpoint are converted into JSON. You can use the WP_REST_Response object , this wraps normal body data and allows you to return a custom status code.

function your_endpoint( $data ) {
    $posts = get_posts( array(
         'author' => $data['your_parameter'],
    ) );

    if ( empty( $posts ) ) {
        return new WP_Error( 'your_endpoint_no_data', 'No Data', array( 'status' => 404 ) );
    }

    return new WP_REST_Response( $posts, 200 );
}

function your_endpoint( $data ) {

$posts = get_posts( array(

'author' => $data['your_parameter'],

) );

if ( empty( $posts ) ) {

return new WP_Error( 'your_endpoint_no_data', 'No Data', array( 'status' => 404 ) );

}

return new WP_REST_Response( $posts, 200 );

}

Really powerful stuff, that makes it easy to detach WordPress and the actual client using the data provided by it.

You can read more about it here.

Headless WordPress with the HTTP REST API 2.0+

A ROUTE

THE ENDPOINT

RETURN VALUE

Enjoy coding …

Alexander