XML from PHP, how to apply the XSL

I have the code as below , but I cant work out how to apply the XSL file for formatting? Any ideas, Thanks.

<?php header("Content-Type: text/xml"); //set the content type to xml?>
<?php include 'dbconn.php'; // database Conn?>
<?php include 'sql.php'; // SQL?>
<?php
$xmlBody = '<?xml version="1.0" encoding="ISO-8859-1"?>';
$xmlBody .= "<XML>";
while($row = mysql_fetch_array($sql)){
$country = $row["country"];
$xmlBody .= '
<Customers>
<Country>'.$country.'</Country>
</Customers>';
}
mysql_close();
$xmlBody .= "</XML>";
echo $xmlBody;
?>

James Flowers
Crystal Consultant