[eluser]Mark Croxton[/eluser]
Ok, to answer your original question: why not look at the values in the $_POST global: $_POST['my_element[]']?
Or better, use CI's input class: $this->input->post('my_element[]');
EDIT: now you've edited your last post I see what you're trying to do. I believe CI parses those rules with a regular expression so using an array there won't fly. Why not pass as a string with a delimiter and explode() back into an array?