/**
* Returns array defining the 'ISO Week Date' as defined in ISO 8601
*
* Expects a date in the proleptic Gregorian calendar using 'Astronomical'
* year numbering, that is, with a year 0. Algorithm is valid for all
* years (positive and negative).
*
* N.B. the ISO week day no for Sunday is defined as 7, whereas this
* class and its related functions defines Sunday as 0.
*
* @param int $pn_day
* the day of the month
* @param int $pn_month
* the month
* @param int $pn_year
* the year
*
* @return array array of ISO Year, ISO Week No, ISO Day No as
* integers
* @access public
* @static
*
* @since Method available since Release 1.5.0
*/
static function isoWeekDate($pn_day = 0, $pn_month = 0, $pn_year = null)
{
if (is_null($pn_year)) {
$pn_year = Calc::dateNow('%Y');
}
if (empty($pn_month)) {
$pn_month = Calc::dateNow('%m');
}
if (empty($pn_day)) {
$pn_day = Calc::dateNow('%d');
}
$hn_jd = Calc::dateToDays($pn_day, $pn_month, $pn_year);
$hn_wd = Calc::daysToDayOfWeek($hn_jd);
if ($hn_wd == 0) {
$hn_wd = 7;
}
$hn_jd1 = Calc::firstDayOfYear($pn_year);
$hn_day = $hn_jd - $hn_jd1 + 1;
if ($hn_wd <= $hn_jd - Calc::lastDayOfYear($pn_year) + 3) {
// ISO week is the first week of the next ISO year:
//
$hn_year = $pn_year + 1;
$hn_isoweek = 1;
} else {
switch ($hn_wd1 = Calc::daysToDayOfWeek($hn_jd1)) {
case 1:
case 2:
case 3:
case 4:
// Monday - Thursday:
//
$hn_year = $pn_year;
$hn_isoweek = floor(($hn_day + $hn_wd1 - 2) / 7) + 1;
break;
case 0:
$hn_wd1 = 7;
case 5:
case 6:
// Friday - Sunday:
//
if ($hn_day <= 8 - $hn_wd1) {
// ISO week is the last week of the previous ISO year:
//
list($hn_year, $hn_lastmonth, $hn_lastday) = explode(" ", Calc::daysToDate($hn_jd1 - 1, "%Y %m %d"));
list($hn_year, $hn_isoweek, $hn_pisoday) = Calc::isoWeekDate($hn_lastday, $hn_lastmonth, $hn_year);
} else {
$hn_year = $pn_year;
$hn_isoweek = floor(($hn_day + $hn_wd1 - 9) / 7) + 1;
}
break;
}
}
return array((int) $hn_year, (int) $hn_isoweek, (int) $hn_wd);
}