Excel Export Error

Yii 1.1 General Discussion
1 

$model = new User;

			$res = $model->findAll();

			$data[]=array('Name','Email');

			

			foreach($res as $list) 

			{

				$data[]=array($list['username'],$list['email']);

						

			}

			Yii::import('application.extensions.phpexcel.JPhpExcel'); 

                $xls = new JPhpExcel('UTF-8', false, 'test'); 

                $xls->addArray($data); 

                $xls->generateXML('News-letter'.date('Y-m-d'));

I am using the above code to generate excel,

Excel is downloding fine, When I opens it it shows that error , file is in different format specified in the file name,

Can any one help me?