- ( isset($_GET[$env->param("id")])
- && isset($_GET[$env->param("xml")])
- && ($_GET[$env->param("xml")] == "derviation" ? isset($_GET[$env->param("derivation")]) : true)
+ ( !isset($_GET[$env->param("id")])
+ || !isset($_GET[$env->param("xml")])
+ || ($_GET[$env->param("xml")] == "derviation" && !isset($_GET[$env->param("derivation")]))