phpexcel导出问题

今天做phpexcel导出，发现导出如果行（列）超过三四十行（列）就显示发现不可读取的内容。求指教。 ini_set("error_reporting","E_ALL & ~E_NOTICE");
        include_once('PHPExcel/Writer/IWriter.php') ;  
        include_once('PHPExcel/Writer/Excel5.php') ;  
        include_once('PHPExcel.php') ;  
        include_once('PHPExcel/IOFactory.php') ;  
        
        $list = $post_data['list'];
        $totalAll = $post_data['totalAll'];        $obj_phpexcel = new PHPExcel();  
        $obj_phpexcel->getActiveSheet()->getColumnDimension('A')->setWidth(20); 
        $obj_phpexcel->getActiveSheet()->getColumnDimension('B')->setWidth(25); 
        $obj_phpexcel->getActiveSheet()->getColumnDimension('C')->setWidth(20);  
        $obj_phpexcel->getActiveSheet()->getStyle('A1')->applyFromArray(array('font' => array ('size' => '11'),'alignment' => array('horizontal' => PHPExcel_Style_Alignment::HORIZONTAL_CENTER)));  
        $obj_phpexcel->getActiveSheet()->getStyle('B1')->applyFromArray(array('font' => array ('size' => '11'),'alignment' => array('horizontal' => PHPExcel_Style_Alignment::HORIZONTAL_CENTER))); 
        $obj_phpexcel->getActiveSheet()->getStyle('C1')->applyFromArray(array('font' => array ('size' => '11'),'alignment' => array('horizontal' => PHPExcel_Style_Alignment::HORIZONTAL_CENTER)));  
        $obj_phpexcel->getActiveSheet()->getStyle('C3')->applyFromArray(array('font' => array ('size' => '10'),'alignment' => array('horizontal' => PHPExcel_Style_Alignment::HORIZONTAL_CENTER)));   
        $obj_phpexcel->getActiveSheet()->setCellValue('A1','项目编号');  
        $obj_phpexcel->getActiveSheet()->setCellValue('B1','销售机会名称');  
        $obj_phpexcel->getActiveSheet()->setCellValue('C1','本月总成本'); 
        $obj_phpexcel->getActiveSheet()->mergeCells('A1:A3');  
        $obj_phpexcel->getActiveSheet()->mergeCells('B1:B3');  
        $obj_phpexcel->getActiveSheet()->mergeCells('C1:C2');  
        $obj_phpexcel->getActiveSheet()->getStyle('C3')->applyFromArray(array('font' => array ('size' => '10'),'alignment' => array('horizontal' => PHPExcel_Style_Alignment::HORIZONTAL_CENTER)));   
        $obj_phpexcel->getActiveSheet()->setCellValue('C3',$totalAll);          if($list){ 
          $i =4;
          foreach ($list as  $value) {  
            $obj_phpexcel->getActiveSheet()->getStyle('A'.$i)->applyFromArray(array('font' => array ('size' => '10'),'alignment' => array('horizontal' => PHPExcel_Style_Alignment::HORIZONTAL_CENTER)));  
            $obj_phpexcel->getActiveSheet()->getStyle('C'.$i)->applyFromArray(array('font' => array ('size' => '10'),'alignment' => array('horizontal' => PHPExcel_Style_Alignment::HORIZONTAL_CENTER)));  
            $obj_phpexcel->getActiveSheet()->setCellValue('A'.$i,$value['potentials_id']);  
            $obj_phpexcel->getActiveSheet()->setCellValue('B'.$i,$value['potentials_name']);  
            $obj_phpexcel->getActiveSheet()->setCellValue('C'.$i,round($value['total'],2));  
            $i++; 
          }  
        }
        $filename = "项目成本.xls";  
        $filename = iconv("utf-8", 'gbk', $filename);
        $obj_Writer = PHPExcel_IOFactory::createWriter($obj_phpexcel,'Excel5'); 
        header ( 'Content-Type: application/vnd.ms-excel' );
        header ( "Content-Disposition: attachment;filename=$filename" );
        header ( 'Cache-Control: max-age=0' );
        $obj_Writer->save('php://output');exit;