<?php

class Register extends Guest_Controller {

	function Register() {
		parent::Guest_Controller();
		$this->load->helper('form');
		$this->load->library('validation');
	}
	
	function index() {
		// Setup some rules.
....
		$rules['verify'] = "trim|xss_clean|callback_verify_checkbox";
	
		$this->validation->set_rules($rules);
.....
	}
	
	function verify_checkbox($str) {
		if(!isset($str)) {
			$this->validation->set_message('verify_checkbox', 'zomg error!');
			return false;
		} else {
			return true;
		}

	}
	
}
?>