php导出excel中，若数据库一列内容中存在换行，则在excel中对应换成多行，怎么解决

//验证是否已登录
include 'remember_password.php';
	header("Accept-Ranges: bytes");
	header("Content-type: application/vnd.ms-excel");
	header("Content-Disposition: attachment; filename=".$filename);
	include("connect.php");
	$sql="select * from specific_step";
	$query = mysql_query($sql);
	echo "序号\t业务名称\t操作步骤\t备注\t录入人\t录入日期";
	while($row = mysql_fetch_array($query)){
		echo "\n";
		echo $row['serial_number']."\t".$row['name']."\t".$row['step']."\t".$row['other']."\t".$row['input_name'].
		"\t".$row['input_date'];
	}
?>

header("Accept-Ranges: bytes");
header("Content-type: application/vnd.ms-excel");
header("Content-Disposition: attachment; filename=".@$filename);

$ar = array(
  "abcd
123",
  "再来一段
换行
再换行"
);
echo "序号\t备注\n";
foreach($ar as $k=>$v) {
  echo "$k\t\"$v\"\n";
}