Calculating Number of subscribers in PHPList

I want to query the number of subscribers to show it on one my my webpages

Here is what it looks like:

CREATE TABLE `phplist_listuser` (
  `userid` int(11) NOT NULL default '0',
  `listid` int(11) NOT NULL default '0',
  `entered` datetime default NULL,
  `modified` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
  PRIMARY KEY  (`userid`,`listid`),
  KEY `userenteredidx` (`userid`,`entered`),
  KEY `userlistenteredidx` (`userid`,`listid`,`entered`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

Code (markup):

I believe I need to do something like this:

SELECT userid FROM phplist_listuser
WHERE listid=2

Code (markup):

but I forgot how to calculate the number of results returned so I can get the number of subscribers, or is there a more efficient way of doing so?

THANKS


**UPDATE**

After looking a the code of phplist i found this:

$count = Sql_Fetch_Row_Query("select count(*) from {$tables['listuser']} where listid = {$row["id"]} ");

Code (markup):

I guess that would work, but is it efficient?