WP REST API Josh Betz https://josh.blog 

1. What is REST? 2. Using WP REST API 3. Extending WP REST API 4. Examples 5. Discussion 

CHAPTER I What is REST? 

Representational state transfer (REST) or RESTful Web services are one way of providing interoperability between computer systems on the Internet. REST-compliant Web services allow requesting systems to access and manipulate textual representations of Web resources using a uniform and predefined set of stateless operations. https://en.wikipedia.org/wiki/Representational_state_transfer 

Terms • Route/Path • Method • Endpoint • Header • Response Code (Status) 

/wp-json/wp/v2/posts 

• GET • POST • PUT • PATCH • DELETE HTTP Methods 

GET /wp-json/wp/v2/posts 

DELETE /wp-json/wp/v2/posts/470 

HTTP Status Codes • 1xx (Informational responses) • 2xx (Success) • 3xx (Redirection) • 4xx (Client errors) • 5xx (Server errors) 

$ curl -I http://demo.wp-api.org/wp-json/wp/v2/posts/470 HTTP/1.1 200 OK Content-Type: application/json; charset=UTF-8 Connection: keep-alive Access-Control-Allow-Headers: Authorization, Content-Type Access-Control-Expose-Headers: X-WP-Total, X-WP-TotalPages Allow: GET Cache-Control: no-cache, must-revalidate, max-age=0 Date: Wed, 26 Apr 2017 17:21:09 GMT Link: ; rel="alternate"; type=text/html 

CHAPTER II Using WP REST API 

$ curl http://demo.wp-api.org/wp-json/wp/v2/posts/470 | jq .content { "rendered": "

This is a test post!

\n", "protected": false } 

$ curl http://demo.wp-api.org/wp-json | jq .namespaces [ "oembed/1.0", "broker/v1", "liveblog-likes/v1", "wp/v2" ] 

$ curl http://demo.wp-api.org/wp-json | jq .authentication { "oauth1": { "request": "https://demo.wp-api.org/oauth1/request", "authorize": "https://demo.wp-api.org/oauth1/authorize", "access": "https://demo.wp-api.org/oauth1/access", "version": "0.1" }, "broker": "https://demo.wp-api.org/wp-json/broker/v1/connect" } 

$ curl -X POST http://demo.wp-api.org/wp-json/wp/v2/posts -d "post_title=test" | jq . { "code": "rest_cannot_create", "message": "Sorry, you are not allowed to create posts as this user.", "data": { "status": 401 } } 

CHAPTER III Extending WP REST API 

add_action( 'rest_api_init', function () { register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 'methods' => WP_REST_Server::READABLE, // GET 'permission_callback' => function() => { return current_user_can( 'edit_others_posts' ); }, 'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 'args' => array( 'id' => array( 'validate_callback' => function( $param, $request, $key ) { return is_numeric( $param ); } ), ), ) ); } ); 

add_action( 'rest_api_init', function () { register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 'methods' => WP_REST_Server::READABLE, // GET 'permission_callback' => function() => { return current_user_can( 'edit_others_posts' ); }, 'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 'args' => array( 'id' => array( 'validate_callback' => function( $param, $request, $key ) { return is_numeric( $param ); } ), ), ) ); } ); 

add_action( 'rest_api_init', function () { register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 'methods' => WP_REST_Server::READABLE, // GET 'permission_callback' => function() => { return current_user_can( 'edit_others_posts' ); }, 'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 'args' => array( 'id' => array( 'validate_callback' => function( $param, $request, $key ) { return is_numeric( $param ); } ), ), ) ); } ); 

add_action( 'rest_api_init', function () { register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 'methods' => WP_REST_Server::READABLE, // GET 'permission_callback' => function() => { return current_user_can( 'edit_others_posts' ); }, 'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 'args' => array( 'id' => array( 'validate_callback' => function( $param, $request, $key ) { return is_numeric( $param ); } ), ), ) ); } ); 

add_action( 'rest_api_init', function () { register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 'methods' => WP_REST_Server::READABLE, // GET 'permission_callback' => function() => { return current_user_can( 'edit_others_posts' ); }, 'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 'args' => array( 'id' => array( 'validate_callback' => function( $param, $request, $key ) { return is_numeric( $param ); } ), ), ) ); } ); 

add_action( 'rest_api_init', function () { register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 'methods' => WP_REST_Server::READABLE, // GET 'permission_callback' => function() => { return current_user_can( 'edit_others_posts' ); }, 'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 'args' => array( 'id' => array( 'validate_callback' => function( $param, $request, $key ) { return is_numeric( $param ); } ), ), ) ); } ); 

add_action( 'rest_api_init', function () { register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 'methods' => WP_REST_Server::READABLE, // GET 'permission_callback' => function() => { return current_user_can( 'edit_others_posts' ); }, 'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 'args' => array( 'id' => array( 'validate_callback' => function( $param, $request, $key ) { return is_numeric( $param ); } ), ), ) ); } ); 

After your callback is called, the return value is then converted to JSON, and returned to the client. This allows you to return basically any form of data. https://developer.wordpress.org/rest-api/extending-the-rest-api/adding-custom-endpoints/#return-value 

'callback' => function( WP_REST_Request $request ) => { return array( 'success' => true ); }, 

By default, routes receive all arguments passed in from the request… as the first parameter to your endpoint. https://developer.wordpress.org/rest-api/extending-the-rest-api/adding-custom-endpoints/#arguments 

// You can access parameters via direct array access on the object: $param = $request['some_param']; // Or via the helper method: $param = $request->get_param( 'some_param' ); // You can get the combined, merged set of parameters: $parameters = $request->get_params(); // The individual sets of parameters are also available, if needed: $parameters = $request->get_url_params(); $parameters = $request->get_query_params(); $parameters = $request->get_body_params(); $parameters = $request->get_json_params(); $parameters = $request->get_default_params(); // Uploads aren't merged in, but can be accessed separately: $parameters = $request->get_file_params(); 

register_rest_field( 'comment', 'karma', array( 'get_callback' => function( $comment_arr ) { $comment_obj = get_comment( $comment_arr['id'] ); return (int) $comment_obj->comment_karma; }, 'update_callback' => function( $karma, $comment_obj ) { $ret = wp_update_comment( array( 'comment_ID' => $comment_obj->comment_ID, 'comment_karma' => $karma ) ); if ( false === $ret ) { return new WP_Error( 'rest_comment_karma_failed', __( 'Failed to update comment karma.' ), array( 'status' => 500 ) ); } return true; }, ) ); 

register_rest_field( 'comment', 'karma', array( 'get_callback' => function( $comment_arr ) { $comment_obj = get_comment( $comment_arr['id'] ); return (int) $comment_obj->comment_karma; }, 'update_callback' => function( $karma, $comment_obj ) { $ret = wp_update_comment( array( 'comment_ID' => $comment_obj->comment_ID, 'comment_karma' => $karma ) ); if ( false === $ret ) { return new WP_Error( 'rest_comment_karma_failed', __( 'Failed to update comment karma.' ), array( 'status' => 500 ) ); } return true; }, ) ); 

register_rest_field( 'comment', 'karma', array( 'get_callback' => function( $comment_arr ) { $comment_obj = get_comment( $comment_arr['id'] ); return (int) $comment_obj->comment_karma; }, 'update_callback' => function( $karma, $comment_obj ) { $ret = wp_update_comment( array( 'comment_ID' => $comment_obj->comment_ID, 'comment_karma' => $karma ) ); if ( false === $ret ) { return new WP_Error( 'rest_comment_karma_failed', __( 'Failed to update comment karma.' ), array( 'status' => 500 ) ); } return true; }, ) ); 

register_rest_field( 'comment', 'karma', array( 'get_callback' => function( $comment_arr ) { $comment_obj = get_comment( $comment_arr['id'] ); return (int) $comment_obj->comment_karma; }, 'update_callback' => function( $karma, $comment_obj ) { $ret = wp_update_comment( array( 'comment_ID' => $comment_obj->comment_ID, 'comment_karma' => $karma ) ); if ( false === $ret ) { return new WP_Error( 'rest_comment_karma_failed', __( 'Failed to update comment karma.' ), array( 'status' => 500 ) ); } return true; }, ) ); 

register_rest_field( 'comment', 'karma', array( 'get_callback' => function( $comment_arr ) { $comment_obj = get_comment( $comment_arr['id'] ); return (int) $comment_obj->comment_karma; }, 'update_callback' => function( $karma, $comment_obj ) { $ret = wp_update_comment( array( 'comment_ID' => $comment_obj->comment_ID, 'comment_karma' => $karma ) ); if ( false === $ret ) { return new WP_Error( 'rest_comment_karma_failed', __( 'Failed to update comment karma.' ), array( 'status' => 500 ) ); } return true; }, ) ); 

https://developer.wordpress.org/rest-api/ 

CHAPTER IV Examples 

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Thanks Josh Betz https://josh.blog