If you use the extension http://www.yiiframework.com/extension/php-excel-reader/, you might get an error while using it if you do not specify the absolute path to the xls file. The code to read .xls file is the following
$data=new JPhpExcelReader(‘example.xls’);
It should be changed to
$data=new JPhpExcelReader(Yii::app()->getBasePath().’/import/example.xls’);
Yii::app()->getBasePath() return /var/www/projectname/protected. "import" is the folder name where the .xls is kept