Custom endpoint registration in Wordpress - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this WordPress REST API endpoint registration?

Consider the following code that registers a custom REST API endpoint in WordPress. What will be the JSON response when a GET request is made to /wp-json/custom/v1/message?

Wordpress

<?php
add_action('rest_api_init', function () {
  register_rest_route('custom/v1', '/message', [
    'methods' => 'GET',
    'callback' => function () {
      return ['greeting' => 'Hello, world!'];
    },
  ]);
});

A {"message":"Hello, world!"}

B {"greeting":"Hello, world!"}

C 404 Not Found error

D 500 Internal Server Error

💡 Hint

Look at the callback return value and the route path.

The callback returns an array with key 'greeting' and value 'Hello, world!'. WordPress converts this to JSON automatically for the REST API response.

📝 Syntax

intermediate

Which option correctly registers a POST method for a custom REST API endpoint?

You want to register a REST API endpoint in WordPress that accepts POST requests at /wp-json/custom/v1/data. Which code snippet correctly registers this endpoint?

A register_rest_route('custom/v1', '/data', ['methods' => 'post', 'callback' => 'handle_post']);

B register_rest_route('custom/v1', '/data', ['method' => 'POST', 'callback' => 'handle_post']);

C register_rest_route('custom/v1', '/data', ['methods' => ['GET', 'POST'], 'callback' => 'handle_post']);

D register_rest_route('custom/v1', '/data', ['methods' => 'POST', 'callback' => 'handle_post']);

💡 Hint

Check the key name and case sensitivity for HTTP methods.

The key must be 'methods' (plural) and the method name must be uppercase 'POST'. Option D uses correct syntax.

🔧 Debug

advanced

Why does this custom endpoint return a 404 error?

This code registers a custom REST API endpoint, but when accessing /wp-json/custom/v1/info, it returns a 404 error. What is the cause?

Wordpress

<?php
add_action('rest_api_init', function () {
  register_rest_route('custom/v1', 'info', [
    'methods' => 'GET',
    'callback' => function () {
      return ['info' => 'Details here'];
    },
  ]);
});

A The route path is missing a leading slash; it should be '/info'.

B The callback function must be named, anonymous functions are not allowed.

C The 'methods' key should be 'method' (singular).

D The 'rest_api_init' hook is incorrect; it should be 'init'.

💡 Hint

Check the route path format in register_rest_route.

The route path must start with a slash '/' to be recognized correctly. Without it, WordPress does not match the endpoint and returns 404.

❓ state_output

advanced

What is the output of this endpoint with permission callback?

Given this code, what will be the HTTP status code when an unauthenticated user requests /wp-json/custom/v1/secret?

Wordpress

<?php
add_action('rest_api_init', function () {
  register_rest_route('custom/v1', '/secret', [
    'methods' => 'GET',
    'callback' => function () {
      return ['secret' => '42'];
    },
    'permission_callback' => function () {
      return is_user_logged_in();
    },
  ]);
});

A 200 OK with JSON {"secret":"42"}

B 404 Not Found error

C 403 Forbidden error

D 401 Unauthorized error

💡 Hint

Consider what happens when permission_callback returns false.

If permission_callback returns false, WordPress returns 403 Forbidden, not 401 or 404.

🧠 Conceptual

expert

Which statement about custom REST API endpoint registration in WordPress is TRUE?

Select the one correct statement about registering custom REST API endpoints in WordPress.

A The 'rest_api_init' action must be used to register endpoints, and the route path must start with a slash.

B Endpoints can be registered anytime during the page load, even before 'init' hook.

C The 'callback' function must always return a WP_Error object for successful responses.

D Permission callbacks are optional but if omitted, the endpoint is always accessible.

💡 Hint

Think about when and how endpoints are registered and route path format.

Endpoints must be registered on 'rest_api_init' hook, and route paths require a leading slash. Permission callbacks are optional but if omitted, endpoint is accessible. Callback returns data, not WP_Error for success.