Question

My friends and I are creating a petition board and i’m adding a like/dislike function to it. I intend to make it such that only users can like/dislike it. Problem is, I do not know how to ensure that the users do not spam the button multiple times and how to register which user has liked/disliked which topic. Below is my code so far.

EDIT: Thanks I am creating the likes/dislikes table right now. But now I have to compare the users with the database to see if they have previously liked a comment. I know I have to use WHERE (to check both likes and dislikes table) but i am not sure how to combine it with IF.

<?php
include connect.php

if (isset($_POST['like']) || isset($_POST['dislike'])) 
{
    if($_SESSION['signed_in']){
        if (isset($_POST['like'])) {
            $sql="UPDATE 
                    topics
                SET
                    likes=likes+1,
                WHERE
                    id=topic_id";

            echo "You liked it";
        }

        elseif (isset($_POST['dislike'])) {
            $sql="UPDATE 
                    topics
                SET
                    dislikes=dislikes+1,
                WHERE
                    id=topic_id";

            echo "You disliked it";
        }
    }
    else{
        echo 'Please log in.'
}

?>

Answer 1

You should have a table of “likes” with the following columns.

“article_id”, “user_id”, the primary key should contain both columns

Every time a user likes an article, INSERT INTO likes VALUES($article_id, $user_id);
It will fail if someones Likes twice, thanks to the primary key.

Every time a user dislikes, DELETE FROM likes WHERE article_id = $article_id AND user_id = $user_id. That will allow the user to like again if he wants.

To get the number of Likes for an article, run a SELECT COUNT(*) as nb_of_likes FROM likes WHERE article_id = $article_id instead of storing the number in the article table.

Makes sense ?