function subscribe($email, $listid)
{
  if(!$email||!$listid||!list_exists($listid)||!subscriber_exists($email))
    return false;

  //if already subscribed exit
  if(subscribed($email, $listid))
    return false;

  if(!db_connect())
    return false;

  $query = "insert into sub_lists values ('$email', $listid)";

  $result = mysql_query($query);
        return $result;
}

function unsubscribe($email, $listid)
{
  if(!$email||!$listid)
    return false;

  if(!db_connect())
    return false;

  $query = "delete from sub_lists where email = '$email' and listid = $listid";

  $result = mysql_query($query);
  return $result;
}