writing XML file from MySQL data - foreach loop?

Dear All
I wish to use java charts to display some time series data that is stored in 
a MySQL database. The time series is the evapotranspiration (average value 
for each day) at a large banana plantation. This will help guide irrigation.

The java charts use an XML file for the data and the formatting.

I have limited the records to 29 days:
$query = "SELECT DATE_FORMAT(dt, '%d-%m-%Y') AS Day, AVG(ET) as ET FROM 
database.tablename WHERE DATE(dt) BETWEEN DATE_SUB(NOW(), INTERVAL 30 DAY) 
AND DATE(NOW()) GROUP BY DATE(dt)";

I use a new DomDocument to format the output.

Once I have the structure of the standard part of the document (calling the 
chart and giving some parameters to it) I want to have a series of strings 
like
        <number>1.7</number>
         <number>1.8</number>
         <number>2.1</number>
        etc for 29 times....

For that purpose I wrote:

$row = $doc->createElement( "row" );
  $chart_data->appendChild( $row );

  $number = $doc->createElement( "number" );
while ($row_etdata = mysql_fetch_array($etdata)){
    $row->appendChild( $number );
$txtnode = $doc->createTextNode("$ET");
$number->appendChild($txtnode);

When I run this or a variant, I get for example <number 1.71.71.71.71.7 for 
29 times /> Half right is still wrong. Have considered serialize but that 
has its own complexities.

Your assistance or guidance on solving this would be much appreciated.
thanks
David Hine