Variable Variable Names?


    userData.rs_item_instance_0 = _root.php_instance_0;
    userData.rs_item_instance_1 = _root.php_instance_1;
    userData.rs_item_instance_2 = _root.php_instance_2;
    userData.rs_item_instance_3 = _root.php_instance_3;
    userData.rs_item_instance_4 = _root.php_instance_4;
    userData.rs_item_instance_5 = _root.php_instance_5;
    userData.rs_item_instance_6 = _root.php_instance_6;
    userData.rs_item_instance_7 = _root.php_instance_7;
    userData.rs_item_instance_8 = _root.php_instance_8;
    userData.rs_item_instance_9 = _root.php_instance_9;
    userData.rs_item_instance_10 = _root.php_instance_10;
    userData.rs_item_instance_11 = _root.php_instance_11;

How do I do this using a loop and variable variable names :D?
Please help :D?