cal_days_in_month is a built in php function
php.net/manual/en/function.cal-days ...
Installation
To get these functions to work, you have to compile PHP with --enable-calendar .
The Windows version of PHP has built-in support for this extension. You do not need to load any additional extensions in order to use these functions.
From http://www.php.net/manual/en/calendar.installation.php
As windows user, I didn't have any problems with that, but it is nice you pointed that out. It's possible to replace cal_days_in_month function with date("t") - equivalent functionality.
I'll update class ASAP.
Michael Schulz - 2011-05-02 11:47:45
Arturs Sosins - 2011-05-02 12:28:10 - In reply to 
