照著老師的代碼運行，居然是錯的？！

代碼

?$dir=dirname(__file__);

?require $dir."/phpexcel/phpexcel.php";

?$objPHPExcel=new PHPExcel();

?$objsheet=$objPhPExcel->getActiveSheet();//此行為第5行

?$objsheet->setTitle("demo");

?$objSheet->setcellValue("A1","姓名")->setCellValue("B1","分數");

?$objWriter=PHPExcel_IOFactory::createWriter($objPHPExcel,"Excel5");

?$objWriter->save("demo.xls");

錯誤提示：Notice: Undefined variable: objPhPExcel in?D:\WWW\demo.php?on line?5