how can i solve double submission form?

when the user clicks the "reload" or "refresh" button, the browser submits the same form fields again.how can i solved this problem.

My code is...

    $name = $_POST['name'];
    $comment = $_POST['comment'];   
    echo $name, $comment;
    if(empty($name)){
        $message = "Name is Required!";
    }else if(empty($comment)){
        $message = "comment is required!";
    }else{
        mysqli_query($con,"INSERT INTO comment (post_id, name, comment, date, time)
        VALUES ('$id', '$name', '$comment', '$date', '$time')");
        $message = "Successfully Saved!";
    }