A convenient script to generate iCalendar (.ics) files on the fly in PHP.

PHPtoICS.php

<?php

function make_ics( $summary = 'test', $datestart = 1481328000, $dateend = '', $address = null, $uri = 'http://google.com', $description = 'Here is some body', $filename = 'event.ics' )
{
	// Variables used in this script:
	//   $summary     - text title of the event
	//   $datestart   - the starting date (in seconds since unix epoch)
	//   $dateend     - the ending date (in seconds since unix epoch)
	//   $address     - the event's address
	//   $uri         - the URL of the event (add http://)
	//   $description - text description of the event
	//   $filename    - the name of this file for saving (e.g. my-event-name.ics)
	//
	// Notes:
	//  - the UID should be unique to the event, so in this case I'm just using
	//    uniqid to create a uid, but you could do whatever you'd like.
	//
	//  - iCal requires a date format of "yyyymmddThhiissZ". The "T" and "Z"
	//    characters are not placeholders, just plain ol' characters. The "T"
	//    character acts as a delimeter between the date (yyyymmdd) and the time
	//    (hhiiss), and the "Z" states that the date is in UTC time. Note that if
	//    you don't want to use UTC time, you must prepend your date-time values
	//    with a TZID property. See RFC 5545 section 3.3.5
	//
	//  - The Content-Disposition: attachment; header tells the browser to save/open
	//    the file. The filename param sets the name of the file, so you could set
	//    it as "my-event-name.ics" or something similar.
	//
	//  - Read up on RFC 5545, the iCalendar specification. There is a lot of helpful
	//    info in there, such as formatting rules. There are also many more options
	//    to set, including alarms, invitees, busy status, etc.
	//
	//      https://www.ietf.org/rfc/rfc5545.txt
	// 1. Set the correct headers for this file
	header('Content-type: text/calendar; charset=utf-8');
	header('Content-Disposition: attachment; filename=' . $filename);
	// 2. Define helper functions
	// Converts a unix timestamp to an ics-friendly format
	// NOTE: "Z" means that this timestamp is a UTC timestamp. If you need
	// to set a locale, remove the "\Z" and modify DTEND, DTSTAMP and DTSTART
	// with TZID properties (see RFC 5545 section 3.3.5 for info)
	//
	// Also note that we are using "H" instead of "g" because iCalendar's Time format
	// requires 24-hour time (see RFC 5545 section 3.3.12 for info).
	function dateToCal($timestamp) {
		return (!empty($timestamp))? date('Ymd\THis', $timestamp) : '';
	}
	// Escapes a string of characters
	function escapeString($string) {
		return preg_replace('/([\,;])/','\\\$1', $string);
	}
	// 3. Echo out the ics file's contents
	echo '
	BEGIN:VCALENDAR
	VERSION:2.0
	PRODID:-//hacksw/handcal//NONSGML v1.0//EN
	CALSCALE:GREGORIAN
	BEGIN:VTIMEZONE
	TZID:America/Los_Angeles
	X-LIC-LOCATION:America/Los_Angeles
	BEGIN:DAYLIGHT
	TZOFFSETFROM:-0800
	TZOFFSETTO:-0700
	TZNAME:PDT
	DTSTART:19700308T020000
	RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
	END:DAYLIGHT
	BEGIN:STANDARD
	TZOFFSETFROM:-0700
	TZOFFSETTO:-0800
	TZNAME:PST
	DTSTART:19701101T020000
	RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
	END:STANDARD
	END:VTIMEZONE
	BEGIN:VEVENT
	DTEND;TZID=America/Los_Angeles:'. dateToCal($dateend) .'
	UID:'. uniqid() .'
	DTSTAMP:'. dateToCal(time()) .'
	LOCATION:'. escapeString($address) .'
	DESCRIPTION:'. escapeString($description) .'
	URL;VALUE=URI:'. escapeString($uri) .'
	SUMMARY:'. escapeString($summary) .'
	DTSTART;TZID=America/Los_Angeles:'. dateToCal($datestart) .'
	END:VEVENT
	END:VCALENDAR
	';

}

// Usage
make_ics( $summary, $start, $end, $location, $url, $description, $filename );

?>