I am trying to use a custom WordPress route and function, but I am getting a route and function not found error. Below is my code but I am not sure where it is breaking:

add_action('rest_api_init', function () {
 register_rest_route( 'boss/v1/latest-quiz-results',array(
            'methods'  => 'GET',
            'callback' => 'get_latest_quiz_results'
function get_latest_quiz_results() {
 $query = $wpdb->prepare(
 "SELECT post_id, 
   5PxenC_learndash_user_activity.activity_id, user_id, course_id
  FROM 5PxenC_learndash_user_activity
 INNER JOIN 5PxenC_learndash_user_activity_meta ON 5PxenC_learndash_user_activity_meta.activity_id = 5PxenC_learndash_user_activity.activity_id
  WHERE 5PxenC_learndash_user_activity_meta.activity_meta_key = 'pass'");
$results = $wpdb->get_results($query);
if (empty($results)) {
return new WP_Error( 'empty_category', 'there is no quiz data', 
array('status' => 404) );


$response = new WP_REST_Response($results);

 return $results;
  • Is that latest-quiz-results/) (the route) just a typo in the question? – Sally CJ Jan 22 '19 at 22:52
  • @SallyCJ sorry, typo issue. now fixed – Joel Scalera Jan 22 '19 at 23:22
  • Check my answer. I hope it helps you. – Sally CJ Jan 23 '19 at 0:29

There are 3 issues with your code:

  1. The proper syntax of registering your custom REST API route, is as follows:

    register_rest_route( $namespace, $base_URL, $args, $override );


    register_rest_route( 'boss/v1', '/latest-quiz-results', array(
        'methods'  => 'GET',
        'callback' => 'get_latest_quiz_results'
    ) );

    Consult the reference for more information.

  2. In the get_latest_quiz_results(), $wpdb is not defined because you're missing global $wpdb; at the top:

    function get_latest_quiz_results() {
        global $wpdb; // Add this.
        return $results;
  3. Also in get_latest_quiz_results(), you incorrectly called wpdb::prepare() — the second parameter is mandatory, and there needs to be at least one placeholder (e.g. %s). So for example:

    $query = $wpdb->prepare( "SELECT ... WHERE 5PxenC_learndash_user_activity_meta.activity_meta_key = %s", 'pass' );

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