PHP generates monthly calendar code_PHP tutorial

/*  
Function Written by Nelson Neoh @3/2004.  
For those who wants to utilize this code, please do not remove this remark.  
If you have done any enhancement to this code, please post the copy at http://www.dev-club.com PHP board.  Thank you.

Function usage: calendar(Month,Year)
*/

function calendar($MM,$YYYY){
    if($MM=="") $MM = date("m");
    if($YYYY=="") $YYYY = date("Y");
    if(checkdate($MM,1,$YYYY)){
        $stringDate = strftime("%d %b %Y",mktime (0,0,0,$MM,1,$YYYY));
        $days = strftime("%d",mktime (0,0,0,$MM+1,0,$YYYY));
        $firstDay = strftime("%w",mktime (0,0,0,$MM,1,$YYYY));
        $lastDay = strftime("%w",mktime (0,0,0,$MM,$days,$YYYY));
        $printDays = $days;
        $preMonth = strftime("%m",mktime (0,0,0,$MM-1,1,$YYYY));
        $preYear = strftime("%Y",mktime (0,0,0,$MM-1,1,$YYYY));
        $nextMonth = strftime("%m",mktime (0,0,0,$MM+1,1,$YYYY));
        $nextYear = strftime("%Y",mktime (0,0,0,$MM+1,1,$YYYY));
        print("");
        print("P");
        print("".strftime("%b %Y",mktime (0,0,0,$MM,1,$YYYY))."");
        print("N");
        print("");
        print("SunMonTueWedThuFriSat");

        $currentDays = 1;
        for($a=1;$a<=5;$a++){
            print("");
            $diffDays = $firstDay-$lastDay;
            if($firstDay>$lastDay && $currentDays ==1 && ($diffDays<>1)){
                for($x=$lastDay;$x>=0;$x--){
                    $printDays = $days-$x;
                    print("$printDays");
                }
                for($z=1;$z<$firstDay-$lastDay;$z++){
                    print(" ");
                }
                for($y=$firstDay;$y<7;$y++){
                    print("$currentDays");
                    $currentDays++;
                }
            } elseif($firstDay!=0 && $currentDays==1){
                for($z=1;$z<=$firstDay;$z++){
                    print(" ");
                }
                for($y=$firstDay;$y<7;$y++){
                    print("$currentDays");
                    $currentDays++;
                }
            } else {
                for($u=1;$u<=7 && $currentDays<=$days;$u++){
                    print("$currentDays");
                    $currentDays++;
                }
            }
            print("");
        }
        print("");
    }
}
?>