Question

I am really suffering here trying to get this ajax call to work, sorry for the massiveness of this question.

The user clicks a button, this initiated an ajax call to add a vote to the database. Here is the file called “addvote.php”:

<?php
session_start();


/* COOKIECHECK START */

setcookie('test', 1, time()+3600);
if(!isset($_GET['cookies'])){
    header("Location:/thought/addvote.php?cookies=true&id=".$_GET['id']."&ans=".$_GET['ans']);
}

if(count($_COOKIE) > 0){
    $cookies=1;
} else {
    $cookies=0;
}

/* COOKIECHECK END */



if($cookies==1) {

    $id=$_GET["id"];
    $vId="v".$id;

if (((isset($_SESSION[$vId]) && ((time() - $_SESSION[$vId]) > 180))) || (!isset($_SESSION[$vId]))) {
    // last vote was more than 3 minutes ago
    $_SESSION[$vId] = time(); // update/create vote time stamp

        //ADD VOTE TO DATABASE

    }
    else {
    echo "You've voted on this already";
    }
}
else {
    echo "Please enable cookies to make your vote count";
}


?>

What is supposed to happen: The user is checked to see if they have cookies enabled. If so, they are allowed to add a vote, if not tell them to enable cookies. If they have cookies enabled, and they havn’t voted already – add a vote, if they have voted already, tell them.

What actually happens: A user who hasn’t voted yet clicks the button, this initiates the ajax call and the vote is successfully added, no message is sent to the user. They then move onto another question and click the vote button, “addvote.php” is initiated, but this time it returns “You’ve voted on this already” AND adds a vote! This makes me thing that the page call is running twice, first it adds the vote, then it tries again (and returns the error).

Maybe it has something to do with the header()??

Every question then returns this same message and adds a vote – unless I wait a while and then it works on the first question and the same thing happens again.

Point of note is:
The GET variables are passed along with the header so that I know which question they’re talking about and whether they clicked no or yes.

Again, apologies, this question is a horrible one.

Answer 1

This will not prevent cheating with voting anyway. To test if user has cookies enabled, you can, for example, set cookie using JavaScript on voting page and check it in PHP. But, obviously, if someone wants to cheat, he or she will remove your cookies manually.

Furthemore, you need to add exit after header() call to make your code work:

setcookie('test', 1, time()+3600);
if(!isset($_GET['cookies'])){
    header("Location:/thought/addvote.php?cookies=true&id=".$_GET['id']."&ans=".$_GET['ans']);
    exit;
}