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upvote.php
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upvote.php
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<?php
session_start();
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === TRUE) {
$user_id = $_SESSION["id"];
$answer_id = $_GET["id"];
require_once('../../mysqli-connect.php');
//check if answer exists
$sql = "SELECT id FROM Answers WHERE id=" . $answer_id;
$result = $conn->query($sql);
if($result) {
//create table if it doesn't exist
$sql = "CREATE TABLE Votes
(
user_id int NOT NULL,
answer_id int NOT NULL,
value int NOT NULL
);";
$conn->query($sql);
//check if user already voted on this answer
$sql = "SELECT * FROM Votes WHERE user_id=" . $user_id . " AND answer_id=" . $answer_id;
$result = $conn->query($sql);
if(mysqli_num_rows($result) > 0) {
if($row = mysqli_fetch_array($result)) {
//if already has an upvote
if($row["value"] == 1) {
$sql = "UPDATE Votes SET value=0 WHERE user_id=" . $user_id . " AND answer_id=" . $answer_id;
$conn->query($sql);
$sql = "UPDATE Answers SET upvotes=upvotes-1 WHERE id=" . $answer_id;
$conn->query($sql);
//echo "Vote changed from upvoted";
}
//has no vote
else if ($row["value"] == 0) {
$sql = "UPDATE Votes SET value=1 WHERE user_id=" . $user_id . " AND answer_id=" . $answer_id;
$conn->query($sql);
$sql = "UPDATE Answers SET upvotes=upvotes+1 WHERE id=" . $answer_id;
$conn->query($sql);
//echo "Vote changed from nothing";
}
//has a downvote
else {
$sql = "UPDATE Votes SET value=1 WHERE user_id=" . $user_id . " AND answer_id=" . $answer_id;
$conn->query($sql);
$sql = "UPDATE Answers SET upvotes=upvotes+1, downvotes = downvotes-1 WHERE id=" . $answer_id;
$conn->query($sql);
//echo "Vote changed from downvote";
}
}
mysqli_free_result($result);
}
//user didn't vote on this answer yet
else {
$sql = "INSERT INTO Votes(user_id, answer_id, value)
VALUES (" . $user_id . ", " . $answer_id . ", 1);";
$conn->query($sql);
$sql = "UPDATE Answers SET upvotes=upvotes+1 WHERE id=" . $answer_id;
$conn->query($sql);
//echo "Added upvote";
}
//echo "ID: " . $user_id . " - Question: " . $answer_id;
} else {
echo "Error: answer doesn't exist";
}
$conn->close();
} else {
echo "Not logged in";
}
?>