Pagination throws form validation error when clicking links

Code:
function search_by_zip_result()

  {

    

    $this->load->library('zipcode_class');

    $vehicle_type     = $this->input->post('vehicle_type_search');

    $vehicle_subtype  = $this->input->post('vehicle_subtype_search');

    $vehicle_make     = $this->input->post('vehicle_make_search');

    $vehicle_model    = $this->input->post('vehicle_model_search');

    $from_price       = $this->input->post('from_price');

    $to_price         = $this->input->post('to_price');

    $from_year        = $this->input->post('from_year');

    $to_year          = $this->input->post('to_year');

    $radius           = $this->input->post('radius');

    $zip              = $this->input->post('search_by_zip');





    $this->form_validation->set_rules('search_by_zip', 'Zip Code', 'trim|required|min_length[5]|max_length[5]|integer|xss');

    $this->form_validation->set_rules('from_price', 'Price From', 'trim|integer|xss');

    $this->form_validation->set_rules('to_price', 'Price to', 'trim|integer|xss');

    if($this->form_validation->run() == FALSE)

    {

      echo 'error';

      echo validation_errors();

      exit();

    }



    $lat          = '';

    $lon          = '';

    $city         = '';

    $state        = '';

    $state_prefix = '';



    $lat_lon_rc = $this->_get_lat_long_zip($zip);

    if($lat_lon_rc)

    {

      foreach($lat_lon_rc->result() as $lat_lon_row )

       {

         $lat           = $lat_lon_row->lat;

         $lon           = $lat_lon_row->lon;

         $city          = $lat_lon_row->city;

         $state         = $lat_lon_row->state_name;

         $state_prefix  = $lat_lon_row->state_prefix;

       }

    }

   



   $zips_in_radius = $this->zipcode_class->zipcodeRadius($lat, $lon, $radius);

   if($zips_in_radius)

   {   

     // Now get all the vehicles subimtted within those zip codes.     

     

   

    // Get the count of records for pagination

     $vehicle_result_count = $this->_get_vehicles_in_radius_zip($zips_in_radius,

                                                          $vehicle_type,

                                                          $vehicle_make,

                                                          $vehicle_subtype,

                                                          $vehicle_model,

                                                          $from_year,

                                                          $to_year,

                                                          $from_price,

                                                          $to_price,

                                                          $limit = null ,

                                                          $offset  = null);



    

     if($vehicle_result_count)

     {      

       $config['base_url'] = base_url().'search/search_by_zip_result/';

       $config['total_rows'] = count($vehicle_result_count->result());

       $config['per_page'] = 3;

      

       $limit = $config['per_page'];

       $config['uri_segment'] = 4;

       $offset = $config['uri_segment'];

      

       $vehicle_result_2 = $this->_get_vehicles_in_radius_zip($zips_in_radius,  $vehicle_type, $vehicle_make, $vehicle_subtype, $vehicle_model,

                                                              $from_year, $to_year, $from_price,$to_price,

                                                              $limit, $offset);

    

       $this->pagination->initialize($config);

       

       $subview['page_links'] = $this->pagination->create_links();

      

       $data['menu']              = $this->mylib->get_menu();

       $data['sidebar_content']   = $this->mylib->_load_sidebars();

       $data['page_header']       = 'Click on the ad to see details';

       $subview['search_results'] = $vehicle_result_2;

       $data['search_results']    = $this->load->view('search/results', $subview, TRUE);

       $this->load->view('welcome_message', $data);

     }

     else

     {

       redirect(base_url().'search/search_by_zip_result',

               $this->session->set_flashdata('results_not_found', 'No results for those search criteria.' ));

     }



   }

   else

   {

     echo 'no zips codes ';

     exit();

   }  

 }