Hi, first time poster, and I'm not entirely experienced...

Here is the situation: I am in process of creating a website where users can vote items, much like Digg. I am using MySQL and PHP. In my mysql database, I have two tables, one of them for users and the other for the items which users can vote on.

In order to vote, a user clicks on a link, with the href="voteup.php?id=3" where 3 could be any number - it's the id of the item they are voting on. This vote adds one to the row of the item.

The problem: I don't know how to keep track of what items each user voted on. And since I can't keep track, I cannot prevent them from voting infinitely on each item. Does anyone have any ideas on what I could do to keep track of what items the user votes?

I was considering adding an additional column on the table for the items, with a string of USER IDs, but I'm not entirely sure where to go with that.

Thanks in advance!

If each user will have their own user ID, then that is a perfect idea.

SQL:

create table votes (
   itemid int,
   userid int,
   voteup int
)

Then to prevent multiple votes from the same user:

PHP Code:

$sql = "
   select
      count(*) as uservotes
   from
      votes 
   where
      itemid = {$itemid}
      and userid = {$userid}
";
$sqlresult = mysql_query($sql) or die("Error counting votes.");
$row = mysql_fetch_array($sqlresult);
if $row["uservotes"] >= 1 {
   //this user has already voted on this item
   echo "You silly cat.  You already voted.";
} else {
   //this user has not yet voted
   $sql = "
      insert into votes (
         itemid, 
         userid, 
         voteup
      )
      values (
         {$itemid}, 
         {$userid}, 
         1
      )
   ";
   $sqlresult = mysql_query($sql) or die("Error inserting voteup.");
}