function isValid($id = null){
		$this->db->select('id');
		$this->db->from('products');
		// join on user_id = this->user->id
		$this->db->where('id', $id);
		$query = $this->db->get();
		if($query->num_rows == 0)
		{
			return FALSE;
		}
		else
		{
			return TRUE;
		}
	}