The following SQL query causes an error

SELECT vote_vo_ip, COUNT(*) as times FROM `vote` 
LEFT OUTER JOIN `voter` ON vote.vote_vo_id = voter.vo_id
WHERE vote_co_id = 2
AND times > 1
GROUP BY vote_vo_ip

The column ‘times’ has not been created when we run the WHERE clause, so we have to use HAVING after the WHERE, for example

SELECT vote_vo_ip, COUNT(*) as times FROM `vote` 
LEFT OUTER JOIN `voter` ON vote.vote_vo_id = voter.vo_id
WHERE vote_co_id = '.$co_id.'
GROUP BY vote_vo_ip 
HAVING times > 1

Which works