iCal PHP Parser

iCal.php

<?php
// SOURCE: https://gist.github.com/seebz/c00a38d9520e035a6a8c

class iCal
{
	/**
	 * @var string
	 */
	public $title;

	/**
	 * @var string
	 */
	public $description;

	/**
	 * @var array
	 */
	public $events = array();

	/**
	 * @var array
	 */
	protected $_eventsByDate;


	public function __construct($content = null)
	{
		if ($content) {
			$isUrl = strpos($content, 'http') === 0 && filter_var($content, FILTER_VALIDATE_URL);
			$isFile = strpos($content, "\n") === false && file_exists($content);
			if ($isUrl || $isFile) {
				$content = file_get_contents($content);
			}
			$this->parse($content);
		}
	}


	public function title()
	{
		return $this->summary;
	}

	public function description()
	{
		return $this->description;
	}

	public function events()
	{
		return $this->events;
	}

	public function eventsByDate()
	{
		if (! $this->_eventsByDate) {
			$this->_eventsByDate = array();
			$tmpEventsByDate = array();

			foreach ($this->events() as $event) {
				foreach ($event->occurrences() as $occurrence) {
					$date = date('Y-m-d', $occurrence);
					$newevent = clone $event;
					$newevent->fixOccurringDate($occurrence);
					// generate key for sorting
					$key = strtotime($newevent->dateStart);
					while(isset($tmpEventsByDate[$date][$key])) $key++;
					$tmpEventsByDate[$date][$key] = $newevent;
				}
			}

			// sort array
			ksort($tmpEventsByDate);
			foreach ($tmpEventsByDate as $date => $value) {
				ksort($value);
				$this->_eventsByDate[$date] = $value;
			}

			// prevent duplicates for edited dates in recurring events
			foreach ($this->_eventsByDate as $dateKey => $date) {
				foreach ($date as $event) {
					if(!empty($event->recurrenceId)) {
						$uid = $event->uid;

						foreach ($date as $eventKey => $eventValue) {
							if($eventValue->uid == $uid && (empty($eventValue->recurrenceId))) {
								unset($this->_eventsByDate[$dateKey][$eventKey]);
							}
						}

					}
				}
			}
		}

		return $this->_eventsByDate;
	}

	public function eventsByDateBetween($start, $end, int $limit=NULL)
	{
		if ((string) (int) $start !== (string) $start) {
			$start = strtotime($start);
		}
		$start = date('Y-m-d', $start);

		if ((string) (int) $end !== (string) $end) {
			$end = strtotime($end);
		}
		$end = date('Y-m-d', $end);

		$return = array();
		foreach ($this->eventsByDate() as $date => $events) {
			if ($start <= $date && $date < $end) {
				if(empty($limit) || count($return) <= $limit) {
					$return[$date] = $events;
				}
			}
			if(!empty($limit) && count($return) >= $limit){
				break;
			}
		}

		return $return;
	}

	public function eventsByDateSince($start, int $limit=NULL)
	{
		if ((string) (int) $start !== (string) $start) {
			$start = strtotime($start);
		}
		$start = date('Y-m-d', $start);

		$return = array();
		foreach ($this->eventsByDate() as $date => $events) {
			if ($start <= $date) {
				if(empty($limit) || count($return) <= $limit) {
					$return[$date] = $events;
				}
			}
			if(!empty($limit) && count($return) >= $limit){
				break;
			}
		}

		return $return;
	}

	public function eventsByDateUntil($end, int $limit=NULL)
	{
		if ((string) (int) $end !== (string) $end) {
			$end = strtotime($end);
		}

		$start = date('Y-m-d');
		$end = date('Y-m-d', $end);
		$return = array();
		foreach ($this->eventsByDate() as $date => $events) {
			if ($start <= $date && $end >= $date) {
				if(empty($limit) || count($return) <= $limit) {
					$return[$date] = $events;
				}
			}
			if(!empty($limit) && count($return) >= $limit){
				break;
			}
		}
		return $return;
	}

	public function parse($content)
	{
		$content = str_replace("\r\n ", '', $content);

		// Title
		preg_match('`^X-WR-CALNAME:(.*)$`m', $content, $m);
		$this->title = $m ? trim($m[1]) : null;

		// Description
		preg_match('`^X-WR-CALDESC:(.*)$`m', $content, $m);
		$this->description = $m ? trim($m[1]) : null;

		// Events
		preg_match_all('`BEGIN:VEVENT(.+)END:VEVENT`Us', $content, $m);
		foreach ($m[0] as $c) {
			$this->events[] = new iCal_Event($c);
		}

		return $this;
	}
}



class iCal_Event
{
	/**
	 * @var string
	 */
	public $uid;

	/**
	 * @var string
	 */
	public $summary;

	/**
	 * @var string
	 */
	public $description;

	/**
	 * @var string
	 */
	public $dateStart;

	/**
	 * @var string
	 */
	public $dateEnd;

	/**
	 * @var string
	 */
	public $recurrenceId;

	/**
	 * @var array
	 */
	public $exdate = array();

	/**
	 * @var stdClass
	 */
	public $recurrence;

	/**
	 * @var string
	 */
	public $location;

	/**
	 * @var string
	 */
	public $status;

	/**
	 * @var string
	 */
	public $created;

	/**
	 * @var string
	 */
	public $updated;

	/**
	 * @var integer
	 */
	protected $_timeStart;

	/**
	 * @var integer
	 */
	protected $_timeEnd;

	/**
	 * @var integer
	 */
	protected $_recurrenceId;

	/**
	 * @var array
	 */
	protected $_occurrences;


	public function __construct($content = null)
	{
		if ($content) {
			$this->parse($content);
		}
	}


	public function summary()
	{
		return $this->summary;
	}

	public function title()
	{
		return $this->summary;
	}

	public function description()
	{
		return $this->description;
	}

	public function occurrences()
	{
		if (empty($this->_occurrences)) {
			$this->_occurrences = $this->_calculateOccurrences();
		}
		return $this->_occurrences;
	}

	public function duration()
	{
		// if ($this->_timeEnd) {
			return $this->_timeEnd - $this->_timeStart;
		// }
	}

	public function parse($content)
	{
		$content = str_replace("\r\n ", '', $content);

		// UID
		if (preg_match('`^UID:(.*)$`m', $content, $m))
			$this->uid = trim($m[1]);

		// Summary
		if (preg_match('`^SUMMARY:(.*)$`m', $content, $m))
			$this->summary = trim($m[1]);

		// Description
		if (preg_match('`^DESCRIPTION:(.*)$`m', $content, $m))
			$this->description = trim($m[1]);

		// Date start
		if (preg_match('`^DTSTART(?:;.+)?:([0-9]+(T[0-9]+Z?)?)`m', $content, $m)) {
			$this->_timeStart = strtotime($m[1]);
			$this->dateStart = date('Y-m-d H:i:s', $this->_timeStart);
		}

		// Date end
		if (preg_match('`^DTEND(?:;.+)?:([0-9]+(T[0-9]+Z?)?)`m', $content, $m)) {
			$this->_timeEnd = strtotime($m[1]);
			$this->dateEnd = date('Y-m-d H:i:s', $this->_timeEnd);
		}

		// Recurrence-Id
		if (preg_match('`^RECURRENCE-ID(?:;.+)?:([0-9]+(T[0-9]+Z?)?)`m', $content, $m)) {
			$this->_recurrenceId = strtotime($m[1]);
			$this->recurrenceId = date('Y-m-d H:i:s', $this->_recurrenceId);
		}

		// Exdate
		if (preg_match_all('`^EXDATE(;.+)?:([0-9]+(T[0-9]+Z?)?)`m', $content, $m)) {
			foreach ($m[2] as $dates) {
				$dates = explode(',', $dates);
				foreach ($dates as $d) {
					$this->exdate[] = date('Y-m-d', strtotime($d));
				}
			}
		}

		// Recurrence
		if (preg_match('`^RRULE:(.*)`m', $content, $m)) {
			$rules = (object) array();
			$rule = trim($m[1]);

			$rule = explode(';', $rule);
			foreach ($rule as $r) {
				list($key, $value) = explode('=', $r);
				$rules->{ strtolower($key) } = $value;
			}

			if (isset($rules->until)) {
				$rules->until = date('Y-m-d H:i:s', strtotime($rules->until));
			}
			if (isset($rules->count)) {
				$rules->count = intval($rules->count);
			}
			if (isset($rules->interval)) {
				$rules->interval = intval($rules->interval);
			}
			if (isset($rules->byday)) {
				$rules->byday = explode(',', $rules->byday);
			}

			// Avoid infinite recurrences
			if (! isset($rules->until) && ! isset($rules->count)) {
				$rules->count = 500;
			}

			$this->recurrence = $rules;
		}


		// Location
		if (preg_match('`^LOCATION:(.*)$`m', $content, $m))
			$this->location = trim($m[1]);

		// Status
		if (preg_match('`^STATUS:(.*)$`m', $content, $m))
			$this->status = trim($m[1]);


		// Created
		if (preg_match('`^CREATED:(.*)`m', $content, $m))
			$this->created = date('Y-m-d H:i:s', strtotime(trim($m[1])));

		// Updated
		if (preg_match('`^LAST-MODIFIED:(.*)`m', $content, $m))
			$this->updated = date('Y-m-d H:i:s', strtotime(trim($m[1])));

		return $this;
	}

	public function isRecurrent()
	{
		return ! empty($this->recurrence);
	}

	public function fixOccurringDate($timestamp)
	{
		if($timestamp != $this->_timeStart) {
			// calculate correct start & end date if not a repeating event
			$duration = $this->duration();

			// get date from occurrences
			$timestampCalc = new DateTime();
			$timestampCalc->setTimestamp($timestamp);

			// make new startdate and start timestamp
			$startCalc = new DateTime();
			$startCalc->setTimestamp($this->_timeStart);
			$startCalc->setDate($timestampCalc->format('Y'), $timestampCalc->format('m'), $timestampCalc->format('d'));
			$this->_timeStart = $startCalc->getTimestamp();
			$this->dateStart = date('Y-m-d H:i:s', $this->_timeStart);

			// calculate end date and time with duration of original event.
			$this->_timeEnd += - $this->_timeStart + $duration;
			$this->dateEnd = date('Y-m-d H:i:s', $this->_timeEnd);
		}
	}

	protected function _isExdate($date)
	{
		if ((string) (int) $date != $date) {
			$date = strtotime($date);
		}
		$date = date('Y-m-d', $date);

		return in_array($date, $this->exdate);
	}

	protected function _calculateOccurrences()
	{
		$occurrences = array($this->_timeStart);

		if ($this->isRecurrent())
		{
			$freq = $this->recurrence->freq;
			$count = isset($this->recurrence->count) ? $this->recurrence->count : null;
			$until = isset($this->recurrence->until) ? strtotime($this->recurrence->until) : null;

			$callbacks = array(
				'YEARLY' => '_nextYearlyOccurrence',
				'MONTHLY' => '_nextMonthlyOccurrence',
				'WEEKLY' => '_nextWeeklyOccurrence',
				'DAILY' => '_nextDailyOccurrence'
			);
			$callback = $callbacks[$freq];

			$offset = $this->_timeStart;
			$continue = $until ? ($offset < $until) : ($count > 1);
			while ($continue) {
				if(isset($occurrence)) {
					if (! $this->_isExdate($occurrence)) {
						$occurrences[] = $occurrence;
						$count--;
					}

				}
				$occurrence = $this->{$callback}($offset);

				$offset = $occurrence;

				$continue = $until ? ($offset < $until) : ($count > 1);
			}
		}

		if ($this->_isExdate($occurrences[0])) {
			unset($occurrences[0]);
			$occurrences = array_values($occurrences);
		}

		return $occurrences;
	}

	protected function _nextYearlyOccurrence($offset)
	{
		$interval = isset($this->recurrence->interval)
			? $this->recurrence->interval
			: 1;

		return strtotime("+{$interval} year", $offset);
	}

	protected function _nextMonthlyOccurrence($offset)
	{
		$dayname = array(
			'MO' => 'monday',
			'TU' => 'tuesday',
			'WE' => 'wednesday',
			'TH' => 'thursday',
			'FR' => 'friday',
			'SA' => 'saturday',
			'SU' => 'sunday'
		);

		$interval = isset($this->recurrence->interval)
			? $this->recurrence->interval
			: 1;

		// INTERVAL IS BY (COUNT)DAYNAME
		if(isset($this->recurrence->byday)){
			$dates = array();
			foreach ($this->recurrence->byday as $pattern) {
				$offsetDateTime = new DateTime();
				$offsetDateTime->setTimestamp((int) $offset);

				preg_match('`([-]?\d+)?(MO|TU|WE|TH|FR|SA|SU)`m', $pattern, $m);
				$recurrenceOffset = (isset($m[1])) ? (int) $m[1] : 1;
				$recurrenceDay = strtr($m[2], $dayname);

				$forDateTime = clone $offsetDateTime;

				for (
					$month = (int) $offsetDateTime->format('Ym');
					$month <= date('Ym', strtotime('+' . $interval*12 . ' months'));
					$month = (int) $forDateTime->modify('+'.$interval.' months')->format('Ym')
				) {
					$yearMonth = $forDateTime->format('Y-m');
					$firstDay = new DateTime('first '. $recurrenceDay . ' of ' . $yearMonth);
					$lastDay = new DateTime('last '. $recurrenceDay . ' of ' . $yearMonth);

					$newDate = $firstDay;

					$daysInMonth = array();
					while ($newDate->getTimestamp() <= $lastDay->getTimestamp()) {
						$daysInMonth[] = $newDate->getTimestamp();
						$newDate->modify('next '. $recurrenceDay);
					}

					if($recurrenceOffset < 0) {
						$dates[] = $daysInMonth[count($daysInMonth) + $recurrenceOffset];
					} else {
						$dates[] = $daysInMonth[$recurrenceOffset - 1];
					}
				}
			}
			sort($dates);

			foreach ($dates as $date) {
				if ($date > $offset) {
					return $date;
				}
			}
		}

		// INTERVAL IS BY DAYNUMBER OF MONTH
		$bymonthday = isset($this->recurrence->bymonthday)
			? explode(',', $this->recurrence->bymonthday)
			: array(date('d', $offset));

		$start = strtotime(date('Y-m-01 H:i:s', $offset));

		$dates = array();
		foreach ($bymonthday as $day) {
			// this month
			$dates[] = strtotime(($day-1) . ' day', $start);

			// next 'interval' month
			$tmp = strtotime("+{$interval} month", $start);
			$time = strtotime(($day-1) . ' day', $tmp);
			if ((string) (int) date('d', $time) == (int) $day) {
				$dates[] = $time;
			}

			// 2x 'interval' month
			$interval *= 2;
			$tmp = strtotime("+{$interval} month", $start);
			$time = strtotime(($day-1) . ' day', $tmp);
			if ((string) (int) date('d', $time) === (int) $day) {
				$dates[] = $time;
			}
		}
		sort($dates);

		foreach ($dates as $date) {
			if ($date > $offset) {
				return $date;
			}
		}
	}

	protected function _nextWeeklyOccurrence($offset)
	{
		$interval = isset($this->recurrence->interval)
			? $this->recurrence->interval
			: 1;

		$byday = isset($this->recurrence->byday)
			? $this->recurrence->byday
			: array( substr(strtoupper(date('D', $offset)), 0, 2) );

		$start = date('l', $offset) !== 'Monday'
			? strtotime('last monday', $offset)
			: $offset;

		$daysname = array(
			'MO' => 'monday',
			'TU' => 'tuesday',
			'WE' => 'wednesday',
			'TH' => 'thursday',
			'FR' => 'friday',
			'SA' => 'saturday',
			'SU' => 'sunday',
		);

		$dates = array();
		foreach ($byday as $day) {
			$dayname = $daysname[$day];

			// this week
			$dates[] = strtotime($dayname, $start);

			// next 'interval' week
			$tmp = strtotime("+{$interval} week", $start);
			$time = strtotime($dayname, $tmp);
			$dates[] = $time;
		}
		sort($dates);

		foreach ($dates as $date) {
			if ($date > $offset) {
				return $date;
			}
		}
	}

	protected function _nextDailyOccurrence($offset)
	{
		$interval = isset($this->recurrence->interval)
			? $this->recurrence->interval
			: 1;

		return strtotime("+{$interval} day", $offset);
	}
}

usage.php

<?php

include 'iCal.php';


$file = 'http://www.google.com/calendar/ical/ht3jlfaac5lfd6263ulfh4tql8%40group.calendar.google.com/public/basic.ics';
$iCal = new iCal($file);


$events = $iCal->eventsByDate();
// or :
// $events = $iCal->eventsByDateBetween('2014-01-01', '2015-01-01');
// or :
// $events = $iCal->eventsByDateSince('2014-01-01');
// or :
// $events = $iCal->eventsByDateSince('today');
// or :
// $events = $iCal->eventsByDateUntil('+30 days');
// in addition, every function starting with eventsBy... can be extended with another variable with a limit on the amount of events.
// for example:
// $events = $iCal->eventsByDateUntil('+30 days', 10);

foreach ($events as $date => $events)
{
	echo $date . "\n";
	echo '----------' . "\n";

	foreach ($events as $event)
	{
		echo '* ' . $event->title() . "\n";
	}

	echo "\n";
}

Thanks @mlongoria1 - that was flummoxing me too!