/**
  * Get the SQL LIMIT segment for this feed.
  *
  * Depending on settings it can be LIMIT <num> or empty.
  * 
  * @return string
  */
 public function get_post_limit_sql($posts_per_page = false)
 {
     if ($posts_per_page === false) {
         $posts_per_page = (int) $this->limit_items;
     }
     if ($posts_per_page === self::ITEMS_WP_LIMIT) {
         $posts_per_page = (int) get_option('posts_per_rss');
     }
     if ($posts_per_page > 0) {
         return $posts_per_page;
     }
     // no limit
     if ($posts_per_page === self::ITEMS_NO_LIMIT) {
         return '';
     }
     if ($posts_per_page === self::ITEMS_GLOBAL_LIMIT) {
         $podcast = Podcast::get();
         if ((int) $podcast->limit_items !== self::ITEMS_GLOBAL_LIMIT) {
             return $this->get_post_limit_sql($podcast->limit_items);
         }
     }
     // default to no limit; however, this should never happen
     return '';
 }