PHPFUI/InstaDoc
 
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<?php

/**
 * Create timezone data for use in icalendar file
 *
 * @author	Dan Cogliano <http://zcontent.net>
 * @copyright   Copyright (C) 2006 - 2018 by Dan Cogliano
 * @license     GNU GPLv3 <http://www.gnu.org/licenses/gpl.html>
 * @link http://phpfui.com/?n=ICalendarOrg
 */

namespace ICalendarOrg;

/**
 * Zap Calendar Time Zone Helper Class
 *
 * Class to help create timezone section of iCalendar file
 */
class ZCTimeZoneHelper
	{
	/**
	 * getTZNode creates VTIMEZONE section in an iCalendar file
	 *
	 * @param int $startyear int start year of date range
	 * @param int $endyear int end year of date range
	 * @param string $tzid string PHP timezone, use underscore for multiple words (i.e. 'New_York' for 'New York')
	 * @param $parentnode object iCalendar object where VTIMEZONE will be created
	 *
	 * @return \ICalendarOrg\ZCiCalNode VTIMEZONE object
	 */
	public static function getTZNode(int $startyear, int $endyear, string $tzid, ?ZCiCalNode $parentnode) : \ICalendarOrg\ZCiCalNode
		{
		$tzmins = [];
		$tzmaxs = [];

		$tzmins[$tzid] = $startyear;
		$tzmaxs[$tzid] = $endyear;

		foreach (\array_keys($tzmins)as $tzid)
			{
			$tmin = $tzmins[$tzid] - 1;

			if (\array_key_exists($tzid, $tzmaxs))
				{
				$tmax = $tzmaxs[$tzid] + 1;
				}
			else
				{
				$tmax = $tzmins[$tzid] + 1;
				}
			$tstart = \gmmktime(0, 0, 0, 1, 1, $tmin);
			$tend = \gmmktime(23, 59, 59, 12, 31, $tmax);
			$tz = new \DateTimeZone($tzid);
			$transitions = $tz->getTransitions($tstart, $tend);
			$tzobj = new \ICalendarOrg\ZCiCalNode('VTIMEZONE', $parentnode, true);
			$datanode = new \ICalendarOrg\ZCiCalDataNode('TZID:' . \str_replace('_', ' ', $tzid));
			$tzobj->data[$datanode->getName()] = $datanode;
			$count = 0;
			$lasttransition = null;

			if (1 == \count($transitions))
				{
				// not enough transitions found, probably UTC
				// lets add fake transition at end for those systems that need it (i.e. Outlook)

				$t2 = [];
				$t2['isdst'] = $transitions[0]['isdst'];
				$t2['offset'] = $transitions[0]['offset'];
				$t2['ts'] = $tstart;
				$t2['abbr'] = $transitions[0]['abbr'];
				$transitions[] = $t2;
				}

			foreach ($transitions as $transition)
				{
				$count++;

				if (1 == $count)
					{
					$lasttransition = $transition;

					continue; // skip first item
					}

				if (1 == $transition['isdst'])
					{
					$tobj = new \ICalendarOrg\ZCiCalNode('DAYLIGHT', $tzobj);
					}
				else
					{
					$tobj = new \ICalendarOrg\ZCiCalNode('STANDARD', $tzobj);
					}

				// convert timestamp to local time zone
				$ts = \ICalendarOrg\ZDateHelper::toUnixDateTime(\ICalendarOrg\ZDateHelper::toLocalDateTime(\ICalendarOrg\ZDateHelper::toSQLDateTime($transition['ts']), $tzid));
				$datanode = new \ICalendarOrg\ZCiCalDataNode('DTSTART:' . \ICalendarOrg\ZDateHelper::toiCalDateTime($ts));
				$tobj->data[$datanode->getName()] = $datanode;
				$toffset = $lasttransition['offset'];
				$thours = (int)($toffset / 60 / 60);
				$tmins = \abs($toffset) / 60 - (int)(\abs($toffset) / 60 / 60) * 60;

				if ($thours < 0)
					{
					$offset = \sprintf('%03d%02d', $thours, $tmins);
					}
				else
					{
					$offset = \sprintf('+%02d%02d', $thours, $tmins);
					}
				$datanode = new \ICalendarOrg\ZCiCalDataNode('TZOFFSETFROM:' . $offset);
				$tobj->data[$datanode->getName()] = $datanode;

				$toffset = $transition['offset'];
				$thours = (int)($toffset / 60 / 60);
				$tmins = \abs($toffset) / 60 - (int)(\abs($toffset) / 60 / 60) * 60;

				if ($thours < 0)
					{
					$offset = \sprintf('%03d%02d', $thours, $tmins);
					}
				else
					{
					$offset = \sprintf('+%02d%02d', $thours, $tmins);
					}
				$datanode = new \ICalendarOrg\ZCiCalDataNode('TZOFFSETTO:' . $offset);
				$tobj->data[$datanode->getName()] = $datanode;

				$datanode = new \ICalendarOrg\ZCiCalDataNode('TZNAME:' . $transition['abbr']);
				$tobj->data[$datanode->getName()] = $datanode;

				$lasttransition = $transition;
				}
			}

		return $tzobj;
		}
	}
© 2026 Bruce Wells
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