Hi guys, ok I'm going through this book called "Learning PHP Data Objects". Just saying so there's a reference. Anyway I'm getting the following error when I upload the code below. The page is saved as books.xm.php. Can anyone help me?

Thanks

This page contains the following errors:

error on line 2 at column 1: Extra content at the end of the document

Below is a rendering of the page up to the first error.
HTML Code:
<?php
/*
 * this page lists all of the books we have as an XML data structure
 * PDO LibraryManagement example application
 * @author Dennis Popel
*/

// don't forget the include
include('common.inc.php');
// set the content type to be XML
header('Content-Type: application/xml');
// get the books list
$books = Model::getBooksWithAuthors();

// echo XML declaration and open rot element
echo '<?xml version="1.0"?>', "\n";
echo "<books>\n";

// now iterate over every book and display it
while($b = $books->fetch()){

 ?>
 
 <book id="<?=$b->id?>">
  <isbn><?=$b->isbn?></isbn>
  <title><?=htmlspecialchars($b->title)?></title>
  <publisher><?=htmlspecialchars($b->publisher)?></publisher>
  <summary><?=htmlspecialchars($b->summary)?></summary>
  <author>
   <id><?=$b->author?></id>
   <lastName><?=$b->lastName?></lastName>
   <firstName><?=$b->firstName?></firstName>
  </author>
 </book>
 
 <?php
 
} // end while($b = $books->fetch()){} loop

echo '</books>';

?>