/**
  * Get the users who've registered with this ip address.
  *
  * @param Array $ipaddress IP address to check for
  *
  * @return Array IDs of users who registered with this address.
  */
 static function usersByIP($ipaddress)
 {
     $ids = array();
     $ri = new Registration_ip();
     $ri->ipaddress = $ipaddress;
     if ($ri->find()) {
         while ($ri->fetch()) {
             $ids[] = $ri->user_id;
         }
     }
     return $ids;
 }
 /**
  * Gets the Nth registration with the given IP address.
  *
  * @param string  $ipaddress Address to key on
  * @param integer $n         Nth address
  *
  * @return Registration_ip nth registration or null if not found.
  */
 private function _getNthReg($ipaddress, $n)
 {
     $reg = new Registration_ip();
     $reg->ipaddress = $ipaddress;
     $reg->orderBy('created DESC');
     $reg->limit($n - 1, 1);
     if ($reg->find(true)) {
         return $reg;
     } else {
         return null;
     }
 }