问PHP不显示数据

EN

<?php
        {
            mysql_connect("localhost" , "" , "") or die (mysql_error());
            mysql_select_db("") or die(mysql_error());


            $pid=intval($_SESSION["User_id"]); 
            $query = "SELECT `car`, `details`, `price` FROM `Car``";

            //executes query on the database
            $result = mysql_query ($query) or die ("didn't query");

            //this selects the results as rows
            $num = mysql_num_rows ($result);    


            while($row=mysql_fetch_assoc($result))
            {

                $_SESSION['car'] = $row['car'];
                $_SESSION['details'] = $row['details'];
                $_SESSION['price'] = $row['price'];
            }
        }
        ?>  

        <?php echo $_SESSION['car']; ?>
        <?php echo $_SESSION['details']; ?>
        <?php echo $_SESSION['price']; ?>