生成XML并将其保存到磁盘问题

当我生成XML文件并将其保存到磁盘时，我得到以下错误消息。我得到"XML文档必须有一个顶级元素"。有什么问题吗?谢谢你的帮助。如果我使用

echo sqlToXml($result, "SalesOrder", "sales");

xml数据显示在IE中。但由于某些原因，当我试图保存它时，它抛出了一个错误。

     header("content-type:text/xml");
     $connection = mysql_connect( $db_host, $db_username, $db_password );
    if (!$connection){
    die ("Could not connect to the database: <br />". mysql_error());
    }
    // Select the database
    $db_select=mysql_select_db($db_database);
    if (!$db_select){
    die ("Could not select the database: <br />". mysql_error());
    }
$result = mysql_query("SELECT * from table1");
header("Content-Type: application/xml");
$xmlDocument1 = sqlToXml($result, "SalesOrder", "sales");
$filename= 'c:''xmldoc''results.xml';
file_put_contents($filename ,$xmlDocument1);
function sqlToXml($queryResult, $rootElementName, $childElementName)
{
$xmlData = "<?xml version='"1.0'" encoding='"ISO-8859-1'" ?>'n"; 
$xmlData .= "<" . $rootElementName . ">";
while($record = mysql_fetch_object($queryResult))
{ 
    $xmlData .= "<" . $childElementName . ">";
    for ($i = 0; $i < mysql_num_fields($queryResult); $i++)
    { 
        $fieldName = mysql_field_name($queryResult, $i); 
        $xmlData .= "<" . $fieldName . ">";
        if(!empty($record->$fieldName))
            $xmlData .= $record->$fieldName; 
        else
            $xmlData .= "null"; 
        $xmlData .= "</" . $fieldName . ">"; 
    } 
    $xmlData .= "</" . $childElementName . ">"; 
} 
$xmlData .= "</" . $rootElementName . ">"; 
}

这是结果XML。

 <?xml version="1.0" encoding="ISO-8859-1" ?>
  <SalesOrder>
    <Sales>
     <SalesOrderNumber>SO43</SalesOrderNumber>
     <PurchaseOrderNumber>PO18</PurchaseOrderNumber>
     <AccountNumber>3333</AccountNumber>
     <OrderDate>2001-07-01</OrderDate>
   </Sales>
  </SalesOrder>