Kalender med Mandag som første

//trick to show empty cell in the first row if the month doesn't start from Sunday
if($first_w_of_month==0)
$first_w_of_month=7;
$day = -($first_w_of_month-1);

//geting Numeric representation of the day of the week for first day of the month. 0 (for Sunday) through 6 (for Saturday).
$first_w_of_month = date("w", $first_day_of_month);

//how many rows will be in the calendar to show the dates
if($first_w_of_month==0)
  $first_w_of_month=7;

$total_rows = ceil(($total_days_of_current_month + $first_w_of_month-1)/7);

//trick to show empty cell in the first row if the month doesn't start from Sunday
$day = -($first_w_of_month-1);