我的PHP脚本用于在10月生成日历错误

Question

I made a simple PHP script for generating calendar. It has rounded weeks (I mean if month starts on Friday it will generate it monday of that week), navigation, etc. Works great, but there is a bug in October. It draws last sunday of month twice. I use sundays as a singnal for new row so it makes

Example of my calendar

Example of calendar with October bug

And here the code (I'm not professional, I learned PHP on my own, with no books, just with google and PHP manual):

    <?php
    function getfirstday($month, $year)
    {
        $datestr = "01-$month-$year";
        $day = date('N', strtotime($datestr));
        return $day;
    }

    function getlastday($month, $year)
    {
        $datestr = cal_days_in_month(CAL_GREGORIAN, $month, $year)."-$month-$year";
        $day = date('N', strtotime($datestr));
        return $day;
    }
    //Don't care about this, I just want to have weekdays in my primary language
    function getweekday($weekDay) {
        $list = array();
        $list['1'] = "Pondělí";
        $list['2'] = "Úterý";
        $list['3'] = "Středa";
        $list['4'] = "Čtvrtek";
        $list['5'] = "Pátek";
        $list['6'] = "Sobota";
        $list['7'] = "Neděle";
        return $list[$weekDay];
    }
    //What month and year do we want to show?
    //Ger it from URL or use current
    $month = $_GET['month'];
    if ($month == "") {
        $month = date('m');
    }
    $year = $_GET['year'];
    if ($year == "")  {
        $year = date('Y');
    }
    //Firts day of month
    $startDayStr = "01-$month-$year";
    //Some calculation to get interval of whole month and rounded weeks
    $startDay = strtotime($startDayStr) - (getfirstday($month, $year ) - 1) * 24*60*60;
    $roundMonth = 7 - getlastday($month, $year );
    $limit = cal_days_in_month(CAL_GREGORIAN, $month, $year ) + (getfirstday($month, $year ) - 1) + $roundMonth;
//Some navigation
    ?>
    <table>
        <tr>
          <?php
    if ($month > 1) {
                $prevm = $month - 1;
                $prevh = "cal.php?month=$prevm&year=$year";
            } elseif ($month == 1) {
                $prevm = 12;
                $prevy = $year -1;
                $prevh = "cal.php?month=$prevm&year=$prevy";
            }
            if ($month < 12) {
                $nextm = $month +1;
                $nexth = "cal.php?month=$nextm&year=$year";
            } elseif ($month == 12) {
              $nextm = 1;
              $nexty = $year +1;
              $nexth = "cal.php?month=$nextm&year=$nexty";
            }
            ?>
            <td width="200" align="left"><a href="<?php echo $prevh; ?>">&lt;Previous month</a></td>
            <td  width="190" align="center">
                <?php echo date('m', strtotime("01-$month-$year 00:00:00")); ?>
            </td>
            <td  width="200" align="right"><a href="<?php echo $nexth; ?>">Next month&gt;</a></td>
        </tr>
    </table>
    <?php
    //Let's generate our calendar
    echo "<table border=\"1\"><tr>";
    for($j=1;$j<=7;$j++){
        echo "<td align=\"center\" width=\"85\" height=\"50\"><b>".getweekday($j)."</b></td>";
    }
    echo "</tr><tr>";
    for($i = 1;$i <= $limit;$i++) {
        $lastDayOfMonth = strtotime(cal_days_in_month(CAL_GREGORIAN, $month, $year)."-$month-$year 23:59:59");
        $firstDayOfMonth = strtotime("01-$month-$year");
        $weekDay = date('N', $startDay);
        if ($startDay < $firstDayOfMonth || $startDay > $lastDayOfMonth) {
            $class = "caltdb";
        } else {
            $class = "caltda";
        }
        echo "<td class=\"$class\" align=\"center\" height=\"40\">". date('d', $startDay) ."</td>";


        if ($weekDay == '7') {
            echo "</tr><tr>";
        }
        $startDay = $startDay + 24*60*60;
    }
    echo "</tr></table>";
    ?>

Could you help me fix this problem? I dont know why is it happening.

Thank you a lot, Heretiiik

Answer 1

The problem is likely due to the fact that you're using + 24*60*60 to add one day to a timestamp. This causes problems with daylight saving time, because there are days with 23 or 25 hours when DST begins/ends.

Near the end of your script, replace:

$startDay = $startDay + 24*60*60;

with:

$startDay = strtotime('+1 day', $startDay);