下面是实现的代码：

1. <?php
2.  
3. /**
4.  * PHP+MySQL
5.  * CREATE TABLE IF NOT EXISTS `ip_poll` (
6.  * `ip` varchar(15) NOT NULL,
7.  * `date` datetime NOT NULL
8.  * ) ENGINE=MyISAM DEFAULT CHARSET=latin1;
9.  *
10.  */
11.  
12. function getIP() {
13. $ip=”";
14. if (getenv(“HTTP_CLIENT_IP”)) $ip = getenv(“HTTP_CLIENT_IP”);
15. else if(getenv(“HTTP_X_FORWARDED_FOR”)) $ip = getenv(“HTTP_X_FORWARDED_FOR”);
16. else if(getenv(“REMOTE_ADDR”)) $ip = getenv(“REMOTE_ADDR”);
17. else $ip = “”;
18. return $ip;
19. }
20.  
21. function checkVote()
22. {
23. $ip= getIP();
24. $sql= “select count(*) from ip_poll where ip = ‘”.$ip.”‘ and SUBSTR(date,1,10) = ‘”.date(“Y-m-d”).”‘”;
25. if($res= mysql_query($sql))
26. {
27. $row= mysql_num_rows($res);
28. if($row == 0)
29. {
30. $sqlIns= “insert into ip_poll values (‘”.$ip.”‘,now());”;
31. if(mysql_query($sqlIns))
32. return true;
33. else
34. return false;
35. }else{
36. return false;
37. }
38. }else{
39. return false;
40. }
41. }
42.  
43. ?>