input data form tidak bisa tersimpan ke dalam database namun bisa di submit

Tutorial ini saya dapatkan dari David Insider Forum yang mengunakan CI versi 2 namun saat ini saya mengunakan CI versi 3 sebelumnya saya sudah mencoba menginputkan data lewat codeigniter dan dapat di submit, namun data yang telah di input tersebut tidak masuk ke dalam database

//controller

 <?php
class Store_item_colours extends MX_controller
{

	function __construct() {
	parent:: __construct();
	}

	function submit($update_id)
		{
			if(!is_numeric($update_id)) {
				redirect('site_security/not_allowed');
			}

		$this->load->library('session');
		$this->load->module('site_security');
		$this->site_security->_make_sure_is_admin();

		$update_id = $this->uri->segment(3);
		$submit = $this->input->post('submit', TRUE);
		$colour = trim($this->input->post('colour', TRUE));


		if ($submit="Finished") {
			redirect('store_items/create/'.$update_id);
		}	elseif ($submit=="ubmit") {

			//attempt an insert
			if ($colour!="") {
				$data['item_id'] = $update_id;
				$data['colour'] = $colour;
				$this->_insert($data);

				$flash_msg = "The new colour was successfully added.";
				$value = '<div class="alert alert-success" role="alert">'.$flash_msg.'</div>;';
				$this->session->set_flashdata('item', $value);
			}
		}

		redirect('store_item_colours/update/'.$update_id);

		}

	function update($update_id)
		{
			if(!is_numeric($update_id)) {
				redirect('site_security/not_allowed');
			}

		$this->load->library('session');
		$this->load->module('site_security');
		$this->site_security->_make_sure_is_admin();


		$data['headline'] = "Update Item Colours";
		$data['update_id'] = $update_id;
		$data['flash'] = $this->session->flashdata('item');
		$data['view_file'] = "update";
		$this->load->module("templates");
		$this->templates->admin($data);
	}

	function get($order_by)
	{
	 $this->load->model('mdl_store_item_colours');
	 $query = $this->mdl_store_item_colours->get($order_by);
	 return $query;
 	}
 	//test

 	function get_with_limit($limit, $offset, $order_by)
 	{
 	  $this->load->model('mdl_store_item_colours');
 	  $query = $this->mdl_store_item_colours->get_with_limit($limit, $offset, $order_by);
 	  return $query;
 	}

 	function get_where($id)
 	{
 	  $this->load->model('mdl_store_item_colours');
 	  $query = $this->mdl_store_item_colours->get_where($id);
 	  return $query;
 	}

 	function get_where_custom($col, $value)
 	{
 	  $this->load->model('mdl_store_item_colours');
 	  $query = $this->mdl_store_item_colours->get_where_custom($col, $value);
 	  return $query;
 	}

 	function _insert($data)
 	{
      $this->load->model('mdl_store_item_colours');
      $this->mdl_store_item_colours->_insert($data);
 	}

 	function _update($id, $data)
 	{
 	  $this->load->model('mdl_store_item_colours');
 	  $this->mdl_store_item_colours->_update($id, $data);
 	}

 	function _delete($id)
 	{
 	  $this->load->model('mdl_store_item_colours');
      $this->mdl_store_item_colours->delete($id);
 	}

 	function count_where($column, $value)
 	{
 	  $this->load->model('mdl_store_item_colours');
      $count = $this->mdl_store_item_colours->count_where($column, $value);
 	}

 	function get_max()
 	{
 	  $this->load->model('mdl_store_item_colours');
 	  $max_id = $this->mdl_store_item_colours->get_max();
 	  return $max_id;
 	}

 	function _custom_query($mysql_query)
 	{
 	  $this->load->model('mdl_store_item_colours');
 	  $query = $this->mdl_store_item_colours->_custom_query($mysql_query);
 	  return $query;
 	}
}

//Model

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Mdl_store_item_colours extends CI_Model {
	function __construct() {
	parent::__construct();
	}

	function get_table() {
		$table = "store_item_colours";
		return $table;
	}

	function get($order_by){
		$table = $this->get_table();
		$this->db->order_by($order_by);
		$query = $this->db->get($table);
	return $query;
	}

	function get_with_limit($limit, $offset, $order_by) {
		$table = $this->get_table();
		$this->db->limit($limit, $ffset);
		$this->db->order_by($order_by);
		$query = $this->db->get($table);
	return $query;
	}

	function get_where($col, $value) {
		$table = $this->get_table();
		$this->db->where('id', $id);
		$query = $this->db->get_where($table);
		return $query;
	}

	function get_where_custom($col, $value) {
		$table = $this->get_table();
		$this->db->where($col, $value);
		$query = $this->db->get_where_custom($table);
	return $query;
	}

	function _insert($data){
		$table = $this->get_table();
		$this->db->insert($table, $data);
	}

	function _update($id, $data){
		$table = $this->get_table();
		$this->db->where('id', $id);
		$this->db->update($table, $data);
	}

	function _delete($id){
		$table = $this->get_table();
		$this->db->where('id', $id);
		$this->db->delete($table);
	}

	function count_where($column, $value){
		$table = $this->get_table();
		$this->db->where($column, $value);
		$query = $this->db->get($table);
		$num_rows = $query->num_rows();
	return $num_rows;
	}

	function count_all(){
		$table = $this->get_table();
		$query = $this->db->get($table);
		$num_rows = $query->num_rows();
	return $num_rows;
	}

	function get_max(){
		$table = $this->get_table();
		$this->select_max('id');
		$query = $this->db->get($table);
		$row = $query->row();
		$id = $row->id;
	return $id;
	}

    function _custom_query($mysql_query){
    	$query = $this->db->query($mysql_query);
    	return $query;
    }

 	function item_check($str)

 		{

 		$item_id = url_title($str);
 		$mysql_query = "select * from store_item_colours where item_id='$str' and item_id='$item_id'";
 		$update_id = $this->uri->segment(3);
 		if (is_numeric($update_id)) {
 			//this is an update
 			$mysql_query.=" and id!=$update_id";
 		}

 		$query = $this->_custom_query($mysql_query);
 		$num_rows = $query->num_rows();

 		if ($num_rows>0)
 		{
 			$this->form_validation->set_message('item_check', 'The item title that you submitted is not available');
 			return FALSE;
 		}
 		else
 		{
 			return TRUE;
 		}
 	}

 }

// view //update.php

<h1><?= $headline ?><h1>
<?= validation_errors("<p style='color: red;font-size:12px;line-height:70%'>", "</p>") ?>
<?php
if (isset($flash)) {
	echo $flash;
}
?>
	<div class="row-fluid sortable">
				<div class="box span12">
					<div class="box-header" data-original-title>
						<h2><i class="halflings-icon white edit"></i><span class="break"></span>New Colour Option</h2>
						<div class="box-icon">
							<a href="#" class="btn-minimize"><i class="halflings-icon white chevron-up"></i></a>
							<a href="#" class="btn-close"><i class="halflings-icon white remove"></i></a>
						</div>
					</div>
					<div class="box-content">
						<?php
						$form_location = base_url()."store_item_colours/submit/".$update_id;
						?>
						<form class="form-horizontal" method="post" action="<?= $form_location ?>">
						  <fieldset>
							<div class="control-group">
							  <label class="control-label" for="typeahead">Item Title </label>
							  <div class="controls">
								<input type="text" class="span6" name="colour">
							  </div>
							</div>

							<div class="form-actions">
							  <button type="submit" class="btn btn-primary" name="submit" value="Submit">Submit</button>
							  <button type="submit" class="btn" name="Finished" value="Finished">Finished</button>
							</div>
						  </fieldset>
						</form>

					</div>
				</div><!--/span-->

			</div><!--/row-->

mengapa data yang telah di input bisa ter submit namun tidak tersimpan di database,memang ada data tabel data lain yang telah saya buat "table_items" yang menggunakan function form validation bisa ter submit dan bisa tersimpan di database Mohon pencerahannya mastah :)