Rating: 

If you get the scripts at http://examples.oreilly.com/phphks/

Look for cal2.php in cal directory, it was a review made by Alexander Naumann.
The calendar script works well except in one case :
when the first day of month is a sunday !

To debug, find :
# numeric weekday of the first day in
# the current monthz
$day = jddayofweek( $jd ) - 1;

and just add : if ($day<0){$day=6;}

Finally your file will look this way :

# numeric weekday of the first day in
# the current monthz
$day = jddayofweek( $jd ) - 1; if ($day<0){$day=6;}

Enjoy this great calendar !