รบกวนช่วยดู dynamic select CodeIgniter 2.0.2 ให้หน่อยคับ

product_model.php
<?php
	class Product_model extends CI_Model{
		public $id_type;
		public $id_cate;
		
		function getcate(){
			$this->db->select('id_cate,cate');
			$this->db->from('tbl_cate');
			$query = $this->db->get();
			$categories=array();
			
				if($query->result()){
					foreach ($query->result() as $cates) {
				$categories[$cates->id_cate] = $cates->cate;
				}
			return $categories;
			}else{
			return FALSE;
			}
		}
		function gettype($id_cate){
			$this->db->select('id_type,id_cate,ntype');
			$this->db->from('tbl_type');
			$this->db->where('id_cate',$id_cate);
			//$this->db->order_by('id_type','desc');
			$query = $this->db->get();
			
			$type=array();
			
			if($query->result()){
				foreach($query->result() as $types){
					$type[$types->id_type] = $types->ntype;
				}
				return $type;
			}else{
				return  False;	
				}
			}	
	}

product.php
<?php
	class Product extends CI_controller{
		function form(){
			$this->load->library('ckeditor');
    		$this->load->library('ckFinder');
    		//configure base path of ckeditor folder
   			$this->ckeditor->basePath = base_url().'assets/ckeditor/';
   			$this->ckeditor->config['skin'] = "kama";
    		$this->ckeditor->config['uiColor'] = "#D0E5F5";
   			//Setting a custom toolbar
   			$this->ckeditor->config['width'] = "850px";
    		$this->ckeditor->config['height'] = "300px";
    		//$this->ckeditor->config['toolbar'] ="Full"; 
    		$this->ckediter->config['toolbar']=array(
			array('Source','-','Save','NewPage','DocProps','Preview','Print','-','Templates'),
			array('Cut','Copy','Paste','PasteText','PasteFromWord','-','Undo','Redo'),
			array('Find','Replace','-','SelectAll','-','SpellChecker', 'Scayt'),
			array('Form', 'Checkbox', 'Radio', 'TextField', 'Textarea', 'Select', 'Button', 'ImageButton','HiddenField','/'),
			array('Bold','Italic','Underline','Strike','Subscript','Superscript','-','RemoveFormat'),
			array('NumberedList','BulletedList','-','Outdent','Indent','-','Blockquote','CreateDiv','-','JustifyLeft','JustifyCenter','JustifyRight','JustifyBlock','-','BidiLtr','BidiRtl'),
			array('Link','Unlink','Anchor'),
			array('Image','Flash','Table','HorizontalRule','Smiley','SpecialChar','PageBreak','Iframe','/'),
			array('Styles','Format','Font','FontSize'),
			array('TextColor','BGColor'),
			array('Maximize', 'ShowBlocks','-','About'),
			array('height:600,width:700'));
               
    		$this->ckeditor->config['language'] = 'en';
    		$this->ckfinder->SetupCKEditor($this->ckeditor,'../assets/ckfinder');

			$this->load->model('product_model','t');
			//$data['type']=$this->t->gettype();
			$data['categories']=$this->t->getcate();
			
			$this->load->view('view_head');
        	$this->load->view('view_top_menu');
        	$this->load->view('view_product',$data);
        	$this->load->view('view_footer');	
		}
		function get_type($id_cate){
			header('Content-Type: application/x-json; charset=utf-8');
			echo (json_encode($this->pro_model->gettype($id_cate)));
			
		}
	}

java script

	$(document).ready(function(){       
		$('#categories').change(function()
		{ 
			var id_cate = $('#categories').val();
				$.ajax(
				{
					type: "POST",
					url: "product/get_type/"+id_cate,
					success: function(type)
					{
						$.each(type,function(id_type,ntype)
							{
								var opt = $('<option />');
								opt.val(id_type);
								opt.text(ntype);
								$('#type').append(opt);
							});
					}
				});
		});
	});
</script>

view_product.php
<?php echo form_dropdown('id_cate', $categories, '#', 'id="categories"'); ?>
 <?php echo form_dropdown('id_type', $type, '#', 'id="type"'); ?>