//in third_party librrary PhpExcel
//in library Excel.php:
<?php
if (!defined('BASEPATH')) exit('No direct script access allowed');

require_once APPPATH."/third_party/PHPExcel.php";

class Excel extends PHPExcel {
    public function __construct() {
        parent::__construct();
    }
}
//in controller:
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Welcome extends CI_Controller {

	public function __construct() {
        parent::__construct();
        $this->load->library('Excel');
    }

	public function index(){
		$this->load->view('ReportExcel');
	}

	public function GenerateExcel(){
		$this->excel->setActiveSheetIndex(0);
		$this->excel->getActiveSheet()->setTitle('Prueba reporte excel');
		$count = 1;
		$columns = array('A','B');
		$datos = array(
					array('firstName' => "william1", 'lastName' => "Sulca Talavera William 1"),
					array('firstName' => "william2", 'lastName' => "Sulca Talavera William 2"),
					array('firstName' => "william3", 'lastName' => "Sulca Talavera William 3"),
					array('firstName' => "william4", 'lastName' => "Sulca Talavera William 4"),
					array('firstName' => "william5", 'lastName' => "Sulca Talavera William 5")
				);

		foreach ($datos as $key => $value) {
			$this->excel->getActiveSheet()->setCellValue($columns[0].$count, $value['firstName']);
			$this->excel->getActiveSheet()->setCellValue($columns[1].$count, $value['lastName']);
			$this->excel->getActiveSheet()->getStyle($columns[0].$count)->getAlignment()->setHorizontal(PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
			$this->excel->getActiveSheet()->getStyle($columns[1].$count)->getAlignment()->setHorizontal(PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
			$count++;
		}

		$sheet = $this->excel->getActiveSheet();
		$sheet->getColumnDimension('A')->setAutoSize(true);
		$sheet->getColumnDimension('B')->setAutoSize(true);
		$this->excel->getActiveSheet()->getStyle('A')->getFont()->setSize(11);
		$this->excel->getActiveSheet()->getStyle('B')->getFont()->setSize(11);
		//$this->excel->getActiveSheet()->getStyle('A1')->getFont()->setBold(true);
		//$this->excel->getActiveSheet()->mergeCells('A1:D1');
		$filename='reporte01.xls';
		header('Content-Type: application/vnd.ms-excel');
		header('Content-Disposition: attachment;filename="'.$filename.'"');
		header('Cache-Control: max-age=0');
		$objWriter = PHPExcel_IOFactory::createWriter($this->excel, 'Excel5');
		$objWriter->save('php://output');
	}

}