How to Generate Excel File in Codeigniter using PHPExcel library

<?php
if (!defined('BASEPATH')) exit('No direct script access allowed');
require_once('PHPExcel-1.8/Classes/PHPExcel.php');

class Excel extends PHPExcel
{
public function __construct()
{
parent::__construct();
}
}

?>

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

require_once('PHPExcel-1.8/Classes/PHPExcel/IOFactory.php');
class IOFactory extends PHPExcel_IOFactory
{
public function __construct()
{
parent::__construct();
}
}

?>

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

class Excel_export extends CI_Controller {

function index()
{
$this->load->model("Common_model");
$data["employee_data"] = $this->Common_model->fetch_data();
$this->load->view("excel_list_view", $data);
}

public function excel_view($pid)
{
$id = base64_decode($pid);

$this->load->library("Excel");

$obj = new PHPExcel();
$result = $this->Common->fetch_case_details_excel($id);

$obj->setActiveSheetIndex(0);
// $this->excel->setActiveSheetIndex(0);
$obj->getActiveSheet()->setTitle('Case list');


$table_columns = array("id","first_name","last_name","address","dob","email","mobile","pin");

$column = 0;

foreach($table_columns as $field)
{
$obj->getActiveSheet()->setCellValueByColumnAndRow($column, 1, $field);
$obj->getActiveSheet()->getColumnDimension("D")->setAutoSize(true);
$obj->getActiveSheet()->getColumnDimension("F")->setAutoSize(true);

$obj->getActiveSheet()->getStyle("A1:H1")->getFont()->setBold(true);
//$obj->getActiveSheet()->getStyle("A1:E1")->applyFromArray(array("font" => array("bold" => true)));
$column++;
}



$excel_row = 2;

foreach($result as $row)
{

$obj->getActiveSheet()->setCellValueByColumnAndRow(0, $excel_row, $row->id);
$obj->getActiveSheet()->setCellValueByColumnAndRow(1, $excel_row, $row->first_name);
$obj->getActiveSheet()->setCellValueByColumnAndRow(2, $excel_row, $row->last_name);
$obj->getActiveSheet()->setCellValueByColumnAndRow(3, $excel_row, $row->address);
$obj->getActiveSheet()->setCellValueByColumnAndRow(4, $excel_row, $row->dob);
$obj->getActiveSheet()->setCellValueByColumnAndRow(5, $excel_row, $row->email);
$obj->getActiveSheet()->setCellValueByColumnAndRow(6, $excel_row, $row->mobile);
$obj->getActiveSheet()->setCellValueByColumnAndRow(7, $excel_row, $row->pin);

$excel_row++;
}

// $this->excel->getActiveSheet()->fromArray($result);

$object_writer = PHPExcel_IOFactory::createWriter($obj, 'Excel5');
// $objWriter = PHPExcel_IOFactory::createWriter($this->excel, 'Excel2007');
header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="Data.xls"');
header('Cache-Control: max-age=0'); //no cache
$object_writer->save('php://output');

//save it to Excel5 format (excel 2003 .XLS file), change this to 'Excel2007' (and adjust the filename extension, also the header mime type)
//if you want to save it as .XLSX Excel 2007 format


}

}

<table id="example" class="table table-striped table-bordered" style="width:100%">
<thead style="background-color:#f4f4f4; color:#000;">
<tr>
<th style="width:1%"><center><strong>S.No</strong></center></th>
<th style="width:8%"><center> Id </center></th>
<th style="width:8%"><center>First Name</center></th>
<th style="width:10%"><center>Last Name </center></th>
<th style="width:10%"><center>Address</center></th>
<th style="width:10%"><center>Dob</center></th>
<th style="width:10%"><center>Email </center></th>
<th style="width:10%"><center>Mobile </center></th>
<th style="width:10%"><center>PIN </center></th>

<th style="width:20%"><center>Action</center> </th>
</tr>
</thead>
<tbody>

<?php $i = 1;
foreach($search_result as $row){
?>

<tr>
<td align="center"> <?php echo $i++;?></td>
<td align="center"> <a href="<?php echo base_url()?>Excel_export/view/<?php echo base64_encode($row->id); ?>" target="_blank" > <?php echo $row->file_no; ?> </a></td>
<td align="center"><?php echo $row->id; ?> </td>
<td align="center"><?php echo $row->first_name; ?> </td>
<td align="center"><?php echo $row->last_name; ?> </td>
<td align="center"><?php echo $row->address; ?> </td>
<td align="center"><?php echo $row->dob; ?> </td>
<td align="center"><?php echo $row->mobile; ?> </td>
<td align="center"><?php echo $row->email; ?> </td>
<td align="center"><?php echo $row->pin; ?> </td>



<td>
<!--
<a href="<?php echo base_url()?>Excel_export/view/<?php echo base64_encode($row->id); ?>" target="_blank" class="btn btn-info active navbar-brand"> View </a>
-->

<a href="<?php echo base_url()?>Excel_export/excel_view/<?php echo base64_encode($row->id); ?>" target="_blank" class="btn btn-info active navbar-brand"> Excel </a>


<a href="<?php echo base_url()?>Excel_export/pdfview/<?php echo base64_encode($row->id); ?>" target="_blank" class="btn btn-info active navbar-brand"> PDF </a> </td>
</tr>
<?php } ?>




</tbody>
</table>

function fetch_case_details_excel($id)
{
$this->db->select('*');
$this->db->from('itechxpert');
$this->db->where('id', $id);
$query=$this->db->get();
$result=$query->result();
return $result;
}