Each time I refresh the webpage, the first row added is being duplicated

Question

I'm creating a small comment system, which displays all comments above each other. Problem is that each time I press the submit button the first row added in the database is duplicated. Which results in displaying alot of the same comments. I already try using header and exit, but that didn't worked out either. Could it be maybe have to do with the form action? Thanks in advance.

public function comment($username, $comment)
{
    if (!empty($username) && !empty($comment)) {
        $date = date("Y-m-d H:i:s");
        if ($insert = $this->db->prepare("INSERT INTO reviews (username, comment, time) VALUES (?, ?, ?)")) {
            $insert->bind_param('sss', $username, $comment, $date);
            $insert->execute();
        } else {
            echo "something is wrong with the query";
        }
    } else {
        echo "missing fields";
    }
}

Here is the usage, The form is echo'd below this, as you can see, I redirect to avoid duplication and then exit

$reizen = new reizen;
if (isset($_POST['submit'])) {
    $username = $_POST['username'];
    $comment  = $_POST['comment'];
    header("Location: index.php?" . $_SERVER['QUERY_STRING']);
    $reizen->comment($username, $comment);
    exit();
}
echo $reizen->retrieve();

Answer 1

您需要使用POST / REDIRECT / GET模式来防止这种情况。