problem with a pagerank script

I'm using script at:
http://www.phpbuilder.com/board/showthread.php?t=10378558
and work but this script don't have cache feature
so i
want try to use the folowing script found at:

http://code.google.com/p/popstats/
google_pagerank.class.php
cacher.class.php

i copy in a folder this two file and in another file index.php i insert following:
code:

   <?php
    require_once("google_pagerank.class.php");



$prank = new GooglePageRank("http://www.google.it");



echo $prank->pagerank;
?>

but i got error:

Notice: Couldn't get Pagerank for http:// Got: [] in /home/***/public_html/ttt/google_pagerank.class.php on line 63

any solution?
Thanks