Simple

<?php
session_start();
$_SESSION['iT'] = 1;
header('Location: http://dota-factory.ru/');

// echo $_POST["tr"];



$dbh = 'mysql:dbname=u0082283_dota;host=localhost';
            $user = 'u0082_rever';
            $password = 'u#6o5Hd8';

        try {
            $dbh = new PDO($dbh, $user, $password);
            $dbh->query("SET NAMES 'utf8'");
                } catch (PDOException $e) {
                    echo 'Подключение не удалось: ' . $e->getMessage();
    }

    if (!$dbh) {
        throw new PDOException();
    }

$Trade = $_POST['tr'];




            $stmt = $dbh->prepare("UPDATE `Users` SET `trade` = :Trade WHERE `user_id` = :user_id");
            $stmt->bindParam(':Trade', $Trade);
            $stmt->bindParam(':user_id', $_SESSION['id_vk']);
            $stmt->execute();
?>