dynamic input fields validation in codeigniter

The thing is name like ID2_first_name generate dynamically. have a look at this demo please http://tristandenyer.com/demos/dynamic-form.html

as you can see here this script duplicates the main form, so by using "Add section" option you will get a copy of original form. the name & id values will include the prefix ID2.....IDn

please check the demo using firebug