<?php
$ch = curl_init("http://isbndb.com/api/books.xml?access_key=NF4EFMZP&index1=isbn&results=details&value1=0030839939");
$fp = fopen("book.xml", "w");

curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);

curl_exec($ch);
curl_close($ch);
fclose($fp);

?>