php日期所在月の天数
public function daysOfMonth ($year=NULL,$month=NULL) {
if ($year===NULL) {
$year = $this->getPart('yy') ;
}
if ($month===NULL) {
$month = $this->getPart('mm');
}
if ($month==2)
{
if (($year % 4 == 0 && $year % 100 != 0) || $year %
400 == 0)
$result = 29;
else
$result = 28;
}
elseif ($month == 4 | | $month == 6 || $month == 9 || $month
== 11)
$result = 30;
else
$result = 31;
$result;
}