public static function add_tags_to_feed($id, $tags)
    {
        $dbh = DB::m();
        foreach ($tags as $tag) {
            $tag = mysql_real_escape_string($tag);
            $tag_query_1 = <<<SQL
INSERT
INTO
    hpi_feed_aggregator_tags
SET
    tag = '{$tag}',
    principal = 'no'

SQL;
            $result = mysql_query($tag_query_1, $dbh);
            if ($result) {
                $tag_id = mysql_insert_id($dbh);
            } else {
                if (mysql_errno() == 1062) {
                    #duplicate
                    $tag_id = FeedAggregator_DatabaseHelper::get_tag_id_for_tag_string($tag);
                }
            }
            $tag_id = mysql_real_escape_string($tag_id);
            $tag_query_2 = <<<SQL
INSERT
INTO
    hpi_feed_aggregator_tags_to_feed_links
SET
    tag_id = '{$tag_id}',
    feed_id = '{$id}'

SQL;
            $result = mysql_query($tag_query_2, $dbh);
            if (!$result) {
                if (mysql_errno() == 1062) {
                    #duplicate
                    # Do nothing, link already exists
                }
            }
        }
        return $id;
    }