ICS（iCal）发布/请求/取消

Question

I'm having a lot of trouble getting entries in a .ics file generated from PHP to update. Here's an example of what I'm using:

<?php
header('Content-type: text/calendar; charset=utf-8');
header('Content-Disposition: attachment; filename=calendar.ics');

$time = time();
$dtstamp = date('Ymd', $time). 'T' . date('His', $time) . 'Z'; echo "\r\n";
?>
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//My Event
METHOD:PUBLISH
X-WR-CALNAME:MyCal
BEGIN:VEVENT
DTSTAMP:<?php echo $dtstamp; ?>
ORGANIZER:someone@example.com
SEQUENCE:0
UID:ABC123
DTSTART:20150601T120000
DTEND:20150601T130000
SUMMARY:Event 1 - <?php echo date('His', $time) ."\r\n"; ?>
LOCATION:Location 1
DESCRIPTION:This is Event 1 - <?php echo date('His', $time) ."\r\n"; ?>
END:VEVENT
BEGIN:VEVENT
DTSTAMP:<?php echo $dtstamp; ?>
ORGANIZER:someone@example.com
SEQUENCE:0
UID:DEF123
DTSTART:20150601T160000
DTEND:20150601T170000
SUMMARY:Event 2 - <?php echo date('His', $time) ."\r\n"; ?>
LOCATION:Location 2
DESCRIPTION:This is Event 2 - <?php echo date('His', $time) ."\r\n"; ?>
END:VEVENT
END:VCALENDAR

So this is to output the events to a URL that can be hit in an Android or iOS device and added to the calendar. The next step would be to update the event items when needed. I've been trying to do it with something like this (initial PHP deliberately omitted):

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//My Event
METHOD:PUBLISH
X-WR-CALNAME:MyCal
BEGIN:VEVENT
DTSTAMP:<?php echo $dtstamp; ?>
ORGANIZER:someone@example.com
SEQUENCE:1
UID:ABC123
DTSTART:20150601T123000
DTEND:20150601T130000
SUMMARY:Event 1 - <?php echo date('His', $time) ."\r\n"; ?>
LOCATION:Location 1
DESCRIPTION:This is Event 1 - <?php echo date('His', $time) ."\r\n"; ?>
END:VEVENT
BEGIN:VEVENT
DTSTAMP:<?php echo $dtstamp; ?>
ORGANIZER:someone@example.com
SEQUENCE:1
UID:DEF123
DTSTART:20150601T163000
DTEND:20150601T170000
SUMMARY:Event 2 - <?php echo date('His', $time) ."\r\n"; ?>
LOCATION:Location 2
DESCRIPTION:This is Event 2 - <?php echo date('His', $time) ."\r\n"; ?>
END:VEVENT
END:VCALENDAR

Because the DTSTAMP will always be greater than the previous entry, the sequence has been incremented and the METHOD changed to REQUEST, as far as I can tell that should be enough.

However in Android it just adds the events again, in iOS it displays the events that already exist, with the previous details, and only gives you the option to add the events again. So, I'm wondering what it takes to get the existing events to update, and to later cancel them using METHOD:CANCEL if need be.

Thanks.

Answer 1

What you are trying to do is not possible.

What you probably should be doing, is to create an iCalendar feed. (Usually the webcal:// non-standard URI schema is used for this).

A feed like this should only ever have METHOD:PUBLISH and always contain every single item in the calendar .

To update entries in this feed, you will need to simply update the feed itself. Any items you remove in this feed, are removed from the calendar.

METHOD:CANCEL and METHOD:REQUEST are other iTip methods that are not used in this context. There's two major uses for them:

1. Email invites (aka iMip).
2. CalDAV scheduling

Those methods only really have meaning for iCalendar events that have an ORGANIZER and ATTENDEE s