PHPExcel is a PHP library for reading and writing spreadsheet, csv, excel files. CodeIgniter is one of the well known PHP MVC framework. here is step How to Integrate PHPEXcel library in CodeIgniter.
you can download php excel library form here. Download PHPExcel library.
Unzip or extract the downloaded PHPExcel library files and copy Class directory inside files to application/third-party directory(folder).
Now Call PHPExcel library in Controller where you Needed.
public function __construct()
{
parent::__construct();
require_once APPPATH.'third_party/PHPExcel.php';
$this->excel = new PHPExcel();
}
So, finally install PHPExcel library in Controller.
Now you can use read data form spreadsheet as we as write data to Excel sheet.