PHP Session 封装类

class Session{    function Session()    {        session_start();    }     function set($name, $value)    {        $_SESSION[$name] = $value;    }     function get($name)    {        if(isset($_SESSION[$name]))            return $_SESSION[$name];        else            return false;    }     function del($name)    {        unset($_SESSION[$name]);    }     function destroy()    {        $_SESSION = array();        session_destroy();    }     function save_prefs()    {        global $db, $auth;        $prefs = serialize($this->prefs);        $db->query("UPDATE condra_users SET prefs = '$prefs' WHERE id = '{$auth->id}'");    }}