Hi!
RTMF: here is a quote from the official doc.
cal_days_in_month
(PHP 4 >= 4.1.0)
cal_days_in_month -- Return the number of days in a month for a given year and calendar
Description
int cal_days_in_month ( int calendar, int month, int year)
This function will return the number of days in the month of year for the specified calendar
As you can see the 2nd argument of that function must be an integer, not a string...
BTW, this works fine:
echo cal_days_in_month(0, 4, "2003")."<br>";