Simple XML Output - formatting

hi

i wonder if someone can help

i have some code to make a simple XML output

<?php
header('Content-type: text/xml');
header('Pragma: public');
header('Cache-control: private');
header('Expires: -1');
echo "<?xml version=\"1.0\" encoding=\"utf-8\"?>
<xml>
<customers>
    <id>song_path</id>
    <name>David</name>
    <promos>
    D123OO
    M876TT
    B765DC
    LO122M
    </promos>
</customers>
</xml>";
?>

my problem is;

when the XML is displayed in the browser, it forces the values in <promos> onto 1 line

<promos>D123OO M876TT B765DC LO122M</promos>

is it possible to keep the formatting, so it outputs

<promos>
D123OO
M876TT
B765DC
LO122M
</promos>

i have tried lots of different things but nothing seems to work

\r\n

\n\r

\n

\r

<br />

<p>

the only option which came close was <br />, but the XML actually displays the <br /> tag

can anyone help?

thank you