php 导出页面，不能输出任何其他信息，不能echo print var_dump等，否则，导出EXCEL，，显示无法打开

$this->load->library("PHPExcel");
		$resultPHPExcel = new PHPExcel();
		$resultPHPExcel->getActiveSheet()->setCellValue('A1', '季度'); 
		$resultPHPExcel->getActiveSheet()->setCellValue('B1', '名称'); 
		$resultPHPExcel->getActiveSheet()->setCellValue('C1', '数量'); 

 	$resultPHPExcel->getActiveSheet()->getColumnDimension('A')->setWidth(15);   //设置宽度
 	$resultPHPExcel->getActiveSheet()->getColumnDimension('C')->setWidth(35); 
 	$resultPHPExcel->getActiveSheet()->getColumnDimension('D')->setWidth(15); 
 	$resultPHPExcel->getActiveSheet()->getColumnDimension('E')->setWidth(30); 

		$i = 2; 
		 
		for($j=0;$j<5;$j++){ 
		$resultPHPExcel->getActiveSheet()->setCellValue('A' . $i, $j); 
		$resultPHPExcel->getActiveSheet()->setCellValue('B' . $i, $j); 
		$resultPHPExcel->getActiveSheet()->setCellValue('C' . $i, $j); 



				
		$i ++; 
		}
			$title = "报名概况表";
			$resultPHPExcel->getActiveSheet()->setTitle( $title );

			// Set active sheet index to the first sheet, so Excel opens this as the first sheet
			$resultPHPExcel->setActiveSheetIndex(0);

			// Redirect output to a client’s web browser (Excel2007)
			header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
			header('Content-Disposition: attachment;filename="'.$title.'.xlsx"');
			header('Cache-Control: max-age=0');
			
			$objWriter = PHPExcel_IOFactory::createWriter($resultPHPExcel, 'Excel2007');
			$objWriter->save('php://output');
			exit;


//设置字段类型
		$resultPHPExcel->getActiveSheet()->setCellValueExplicit('C'.$i,$v['z']['shenfenhao'],PHPExcel_Cell_DataType::TYPE_STRING);
        $resultPHPExcel->getActiveSheet()->getStyle('C'.$i)->getNumberFormat()->setFormatCode("@");