Rest Wordpress Rating

function reset_rating($post) {
    $id = $post['ID'];
    $update = $_POST['data key'];
    if ($update === 'Rating') {
        $newrating = $_POST['content'];
        $currentrating = get_post_meta($id, 'Rating');
        if ($newrating != $currentrating) {
            update_post_meta($id, 'Previous Rating', $currentrating);
        }
    }
    return $post;
}
add_filter('wp_insert_post_data', 'reset_rating');