/**
* Determine the number or Tuesdays (or whatever day of the week this date is) since the
* beginning or end of the month.
* @param integer $xth A positive or negative number that determines which weekday of the month we want
* @param string|integer $weekday Either Sunday-Saturday or 0-6 to specify the weekday we want
* @param string|integer $month Either January-December or 1-12 to specify the month we want
* @param integer $year A valid year to specify which year we want
*/
public function getXthWeekdayOfMonth($xth, $weekday = null, $month = null, $year = null)
{
$negpos = substr($xth, 0, 1);
if ($negpos == "+" || $negpos == "-") {
$xth = (int) substr($xth, 1);
} else {
$negpos = "+";
}
if (is_null($weekday)) {
$weekday = $this->getWeekday();
}
if (ctype_digit((string) $weekday)) {
if (!array_key_exists($weekday, $this->weekdays)) {
throw new qCal_Date_Exception_InvalidWeekday("\"{$weekday}\" is not a valid weekday.");
}
} else {
$weekday = strtolower($weekday);
if (!in_array($weekday, $this->weekdays)) {
throw new qCal_Date_Exception_InvalidWeekday("\"{$weekday}\" is not a valid weekday.");
}
$wdays = array_flip($this->weekdays);
$weekday = $wdays[$weekday];
}
if (is_null($month)) {
$month = $this->getMonth();
}
if (ctype_digit((string) $month)) {
if (!array_key_exists($month, $this->months)) {
throw new qCal_Date_Exception_InvalidMonth("\"{$month}\" is not a valid month.");
}
} else {
$month = strtolower($month);
if (!in_array($month, $this->months)) {
throw new qCal_Date_Exception_InvalidMonth("\"{$month}\" is not a valid month.");
}
$mons = array_flip($this->months);
$month = $mons[$month];
}
if (is_null($year)) {
$year = $this->getYear();
}
if (!ctype_digit((string) $year) || strlen($year) != 4) {
throw new qCal_Date_Exception_InvalidYear("\"{$year}\" is not a valid year.");
}
// now, using the year, month and numbered weekday, we need to find the actual day of the month...
$firstofmonth = new qCal_Date($year, $month, 1);
$numdaysinmonth = $firstofmonth->getNumDaysInMonth();
$numweekdays = 0;
// the number of weekdays that have occurred (in the loop)
$foundday = false;
if ($negpos == "+") {
$day = 1;
$wday = $firstofmonth->getWeekday();
// while we are in the current month, loop
while ($day <= $numdaysinmonth) {
// if the specified weekday == the current week day in the loop
if ($weekday == $wday) {
$numweekdays++;
if ($numweekdays == $xth) {
// break out of the loop, we've found the right day! yay!
$foundday = $day;
break;
}
}
if ($wday == 6) {
$wday = 0;
} else {
$wday++;
}
$day++;
}
} else {
$day = $numdaysinmonth;
$lastofmonth = $firstofmonth->getLastDayOfMonth();
$wday = $lastofmonth->getWeekday();
while ($day >= 1) {
if ($weekday == $wday) {
$numweekdays++;
if ($numweekdays == $xth) {
// break out of the loop, we've found the right day! yay!
$foundday = $day;
break;
}
}
if ($wday == 0) {
$wday = 6;
} else {
$wday--;
}
$day--;
}
}
if ($foundday && checkdate($month, $day, $year)) {
$date = new qCal_Date($year, $month, $day);
} else {
if ($day == 32) {
throw new qCal_DateTime_Exception_InvalidDate("You have specified an incorrect number of days for qCal_Date::getXthWeekdayOfMonth()");
} else {
throw new qCal_DateTime_Exception_InvalidDate("You have entered an invalid date.");
}
}
return $date;
}
