function flickr_push_subscriptions_is_valid_topic_id($id)
{
    $map = flickr_push_subscriptions_topic_map();
    if (!isset($map[$id])) {
        return 0;
    }
    if (!$map[$id]['enabled']) {
        return 0;
    }
    return 1;
}
<?php

include "../include/init.php";
loadlib("god");
features_ensure_enabled("flickr_push");
loadlib("flickr_backups");
loadlib("flickr_push");
loadlib("flickr_push_subscriptions");
$topic_map = flickr_push_subscriptions_topic_map();
$GLOBALS['smarty']->assign_by_ref("topic_map", $topic_map);
if ($user_id = get_int32("user_id")) {
    $owner = users_get_by_id($user_id);
    if (!$owner) {
        error_404();
    }
    $GLOBALS['smarty']->assign_by_ref("owner", $owner);
}
$is_backup_user = $owner && flickr_backups_is_registered_user($owner) ? 1 : 0;
$GLOBALS['smarty']->assign("is_backup_user", $is_backup_user);
if ($is_backup_user) {
    $crumb_key = "create_feed";
    $GLOBALS['smarty']->assign("crumb_key", $crumb_key);
    if (post_str("create") && crumb_check($crumb_key)) {
        $topic_id = post_int32("topic_id");
        if (flickr_push_subscriptions_is_valid_topic_id($topic_id)) {
            # HEY LOOK! THIS STILL DOESN'T DEAL WITH FEEDS THAT
            # NEED OR HAVE TOPIC ARGS (20120605/straup)
            # As a practical matter that just means that the
            # API call to register a subscription with
            # Flickr will fail. Since we're already
            # disabling these topics at the template layer I