WP REST API -- How to change HTTP Response status code?

Question

I have a custom endpoint where I want to change HTTP response status to 404 in certain scenarios (e.g post does not exist). How can I do that? Here is an example of custom endpoint:

function af_news_single( \WP_REST_Request $data ) {
    global $wpdb;

    $year = (int) $data['year'];
    $month = (int) $data['month'];
    $day = (int) $data['day'];
    $slug = $data['slug'];

    $date = "{$year}-{$month}-{$day}";

    $news = $wpdb->get_row(
        $wpdb->prepare(
            "SELECT
                DATE_FORMAT(post_date, %s) as `post_date`,
                `post_title`,
                `post_name`,
                `post_content`
             FROM {$wpdb->posts}
             WHERE
                `post_status` = 'publish' AND
                `post_type` = 'post' AND
                `post_name` = %s AND
                `post_date` BETWEEN %s AND %s + INTERVAL 1 DAY
             LIMIT 1
             ", '%Y-%m-%dT%TZ', $slug, $date, $date
        )
    );

    if ( $news ) {
        $news->post_title = qtranxf_translate( $news->post_title );
        $news->post_content = wpautop( qtranxf_translate( $news->post_content ) );
    } else { /* How to change response code? */ }

    return [ 'data' => $news ];
}

How can I change response code in this function?

Answer 1

You can return a WP_Error object in which you define the status code. Here's a snippet from the REST API documentation:

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

    if ( empty( $posts ) ) {
        return new WP_Error( 'awesome_no_author', 'Invalid author', array( 'status' => 404 ) );
    }

    return $posts[0]->post_title;
}

In your case you could do something like:

return new WP_Error( 'page_does_not_exist', __('The page you are looking for does not exist'), array( 'status' => 404 ) );

Answer 2

The simplest way is to do this:

return new WP_REST_Response(null, 404);

Note: this is still a JSON response containing null as the body. You can return a more useful data structure with error codes/messages, etc., or hook into the REST output filters to output a blank text/plain response.

Answer 3

I would not use:

return new WP_REST_Response(null, 404);

I had an issue with hosting provider when I used status codes in this function. Somehow setting status code triggered mod_rewrite response.

Message: Access denied with code 406 (phase 3). Test 'REQUEST_URI|REQUEST_HEADERS|REQUEST_HEADERS_NAMES|ARGS|ARGS_NAMES|REQUEST_BODY' against '!@validateByteRange 0-31' is true.

It might not be and issue with wordpress but using:

return new WP_REST_Response(null);

solved the problem.

I'll just leave it here in case anyone encounters same problem.