A problem with a google PR tool

[OldDarkstarAccount]

found some small PR tool on the web, but it does not seem to work corectly. I get the following error

Warning: file_get_contents(http://www.google.com/search?client=...gfxclass.com): failed to open stream: HTTP request failed! HTTP/1.0 403 Forbidden in /home/content/...../test/php/rank.class.php on line 29

28 and 29 of rank.class.php:

$url = 'http://www.google.com/search?client=navclient-auto&ch=6' . $checksum . '&features=Rank&q=' . $url;
$v = file_get_contents($url);

Can the hosting be the problem ?

[Bagi Zoltán]

Requesting PR nowadays is a huge challange. Could you post here the function which is generates the $checksum variable?