如何确保用户针对特定帖子仅点击我的投票链接一次？

Question

I have a mysql tables...

'users' with uname(a string) as the primary key. 'posts' with id as the primary key.

'posts' has a columnm- 'votes'

When a user is logged in, he can vote posts. The problem is how do i stop him from voting more than once?

Link:(Note: $q is id of the post)

<a href='./vote.php?upid=".$q."'>Upvote</a>

PHP:

if(isset($_GET["upid"])) {
        $plus = $_GET["upid"];
        $query = "UPDATE posts SET votes = votes + 1 WHERE id='$plus'";
        $result = mysqli_query($dbc, $query) or die('Error querying database!');
    }

Answer 1

Take two steps:

1. Onclick set the link's style to display:none. or hide() with jQuery. (UX friendly) (PHP: on future page loads, do not present the link if a vote is already cast by the user.)

2. In your database, save the action in a new/separate table that only allows INSERT only if unique combination of userid and postid. Then you can leverage that table to count the total votes for the post id.

p.s. By storing individual votes using unique post id and user id, you can also allow a user to undo their vote if you wish.