frank

api.php

function get_publisher( WP_REST_Request $request ) {
	$publisher_id = null;
	$params = $request->get_params();
	if (isset($params['id'])) { // get the id parameter
	  $publisher_id = $params['id'];
	};
	// imagine code that gets the record from the database; assuming the code from the database returns $publisher
	if ( empty( $publisher ) ) { // return a 404 response
		return new WP_Error( 'page_does_not_exist', __('The page you are looking for does not exist'), array( 'status' => 404 ) );
	};
  
	return new WP_REST_Response( $publisher ); // return a normal response with the $publisher
}