WordPress Post Voting - Vote once per IP on entire site

Question

I've been researching this for a few days now and found many voting plugins - unfortunately none of them does exactly what I need, so I am trying to hack some functions/scripts that I've found by searching online.

I'm working with this script, now: http://bavotasan.com/2011/a-better-voting-system-for-wordpress/

I'm trying to figure out a way to only allow the IP to vote once on the website. Essentially, if they vote on one post - they cannot vote on another.

This post is similar to this thread, Wordpress Vote Plugin - Vote Once and Track User

add_action("wp_ajax_add_votes_options", "add_votes_options");
add_action("wp_ajax_nopriv_add_votes_options", "add_votes_options");
function add_votes_options() {
if (!wp_verify_nonce($_POST['nonce'], 'voting_nonce'))
    return;

$postid = $_POST['postid'];
$ip = $_POST['ip'];

//$voter_ips = get_post_meta($postid, "voter_ips", true);

// use an option instead

$voter_ips = get_option( "wpse_59080_voter_ips", true );

if(!empty($voter_ips) && in_array($ip, $voter_ips)) {
    echo "null";
    die(0);
} else {
    $voter_ips[] = $ip;
    // update_post_meta($postid, "voter_ips", $voter_ips);
    update_option( "wpse_59080_voter_ips", $voter_ips );

}   

//$current_votes = get_post_meta($postid, "votes", true);
$current_votes = get_option( "wpse_59080_voter_ips", true );

$new_votes = intval($current_votes) + 1;

// update_post_meta($postid, "votes", $new_votes);

// use an option instead

update_option( "wpse_59080_voter_ips", $voter_ips );

$return = $new_votes>1 ? $new_votes." votes" : $new_votes." vote";
echo $return;
die(0);
}

Answer 1

The only difference you need is the place where the IP address will be stored. Instead of a post meta use an option.

So, where the script says …

$voter_ips = get_post_meta($postid, "voter_ips", true);

… use …

$voter_ips = get_option( "wpse_59080_voter_ips", true );

… and where it updates a post meta you should update the option:

update_option( "wpse_59080_voter_ips", $voter_ips );

Answer 2

I ended up doing a direct SQL query on the entire post_meta table, and then displaying the message "VOTED" if the IP address has already been recorded in the DB:

$voter_ips = $_SERVER['REMOTE_ADDR']; 
$result = mysql_query("SELECT * FROM  wp2_postmeta WHERE meta_value LIKE '%$voter_ips%' ");
$num_rows = mysql_num_rows($result);

if ($num_rows > 0){
          $vtext = "VOTED";
          $class = ' class="disabled"';
} else {
$vtext = "VOTE";
$class = "";
}