Tobias Hößl 6186153f68 Second part of refactoring; should be runnable again, yet not thoroughly tested

2012-08-11 08:07:19 +00:00

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SabreTooth VObject library

The VObject library allows you to easily parse and manipulate iCalendar and vCard objects using PHP. The goal of the VObject library is to create a very complete library, with an easy to use API.

This project is a spin-off from SabreDAV, where it has been used for several years. The VObject library has 100% unittest coverage.

Installation

VObject requires PHP 5.3, and should be installed using composer. The general composer instructions can be found on the [composer website](http://getcomposer.org/doc/00-intro.md composer website).

After that, just declare the vobject dependency as follows:

"require" : {
    "sabre/vobject" : "dev-master"
}

Then, run composer.phar update and you should be good. As soon as the first release is out, you should switch dev-master to 2.0.* though.

Usage

Parsing

For our example, we will be using the following vcard:

BEGIN:VCARD
VERSION:3.0
PRODID:-//Sabre//Sabre VObject 2.0//EN
N:Planck;Max;;;
FN:Max Planck
EMAIL;TYPE=WORK:mplanck@example.org
item1.TEL;TYPE=CELL:(+49)3144435678
item1.X-ABLabel:Private cell
item2.TEL;TYPE=WORK:(+49)5554564744
item2.X-ABLabel:Work
END:VCARD

If we want to just print out Max' full name, you can just use property access:


use Sabre\VObject;

$card = VObject\Reader::read($data);
echo $card->FN;

Changing properties

Creating properties is pretty similar. If we like to add his birthday, we just set the property:


$card->BDAY = '1858-04-23';

Note that in the previous example, we're actually updating any existing BDAY that may already exist. If we want to add a new property, without overwriting the previous we can do this with the add method.


$card->add('EMAIL','max@example.org');

Parameters

If we want to also specify that this is max' home email addresses, we can do this with a third parameter:


$card->add('EMAIL', 'max@example'org', array('type' => 'HOME'));

If we want to read out all the email addresses and their type, this would look something like this:

foreach($card->EMAIL as $email) {

    echo $email['TYPE'], ' - ', $email;

}

Groups

In our example, you can see that the TEL properties are prefixed. These are 'groups' and allow you to group multiple related properties together. The group can be any user-defined name.

This particular example as generated by the OS X addressbook, which uses the X-ABLabel to allow the user to specify custom labels for properties. OS X addressbook uses groups to tie the label to the property.

The VObject library simply ignores the group if you don't specify it, so this will work:


foreach($card->TEL as $tel) {
    echo $tel, "\n";
}

But if you would like to target a specific group + property, this is possible too:


echo $card->{'ITEM1.TEL'};

So if you would like to show all the phone numbers, along with their custom label, the following syntax is used:

foreach($card->TEL as $tel) {

    echo $card->{$tel->group . '.X-ABLABEL'}, ": ";
    echo $tel, "\n";

}

Serializing / Saving

If you want to generate your updated VObject, you can simply call the serialize() method.


echo $card->serialize();

Components

iCalendar, unlike vCards always have sub-components. Where vCards are often just a flat list, iCalendar objects tend to have a tree-like structure. For the following paragraphs, we will use the following object as the example:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Sabre//Sabre VObject 2.0//EN
BEGIN:VEVENT
SUMMARY:Curiosity landing
DTSTART:20120806T051439Z
LOCATION:Mars
END:VEVENT
END:VCALENDAR

Since events, tasks and journals are always in a sub component, this is also how we access them.


use Sabre\VObject;

$calendar = VObject\Reader::read($data);
echo $calendar->VEVENT->SUMMARY;

Adding components to a calendar is done with a factory method:


$event = VObject\Component::create('VEVENT');
$calendar->add($event);

$event->SUMMARY = 'Curiosity launch';
$event->DTSTART = '20111126T150202Z';
$event->LOCATION = 'Cape Carnival';

By the way.. cloning also works as expected, as the entire structure is cloned along with it:


$clonedEvent = clone $calendar->VEVENT[0];
$calendar->add($clonedEvent);

Date and time handling

If you ever had to deal with iCalendar timezones, you know it can be complicated. The way timezones are specified is flawed, which is something I may write an essay about some day. VObject does its best to determine the correct timezone. Many standard formats have been tested and verified, and special code has been implemented for special-casing microsoft generated timezone information, and others.

To get a real php DateTime object, you can request this as follows:

$event = $calendar->VEVENT;
$start = $event->DTSTART->getDateTime();
echo $start->format(\DateTime::W3C);

To set the property with a DateTime object, you can use the following syntax:

$dateTime = new \DateTime('2012-08-07 23:53:00', new DateTimeZone('Europe/Amsterdam'));
$event->DTSTART->setDateTime($dateTime, VObject\Property\DateTime::DATE);

The second argument specifies the type of date you're setting. The following three options exist:

LOCAL This is a floating time, with no timezone information. This basically specifies that the event happens in whatever the timezone's currently in. This would be encoded as DTSTART;VALUE=DATE-TIME:20120807235300
UTC This specifies that the time should be encoded as a UTC time. This is encoded as DTSTART;VALUE=DATE-TIME:20120807205300Z. Note the extra Z and the fact that it's two hours 'earlier'.
LOCALTZ specifies that it's supposed to be encoded in its local timezone. For example DTSTART;VALUE=DATE-TIME;TZID=Europe/Amsterdam:20120807235300.
DATE This is a date-only, and does not contain the time. In this case this would be encoded as DTSTART;VALUE=DATE:20120807.

A few important notes:

When a TZID is specified, there should also be a matching VTIMEZONE object with all the timezone information. VObject cannot currently automatically embed this. However, in reality other clients seem to do fine without this information. Yet, for completeness, this will be added in the future.
As mentioned, the timezone-determination process may sometimes fail. Report any issues you find, and I'll be quick to add workarounds!

Recurrence rules

Recurrence rules allow events to recur, for example for a weekly meeting, or an anniversary. This is done with the RRULE property. The RRULE property allows for a LOT of different rules. VObject only implements the ones that actually appear in calendar software.

To read more about RRULE and all the options, check out RFC5545. VObject supports the following options:

UNTIL for an end date.
INTERVAL for for example "every 2 days".
COUNT to stop recurring after x items.
FREQ=DAILY to recur every day, and BYDAY to limit it to certain days.
FREQ=WEEKLY to recur every week, BYDAY to expand this to multiple weekdays in every week and WKST to specify on which day the week starts.
FREQ=MONTHLY to recur every month, BYMONTHDAY to expand this to certain days in a month, BYDAY to expand it to certain weekdays occuring in a month, and BYSETPOS to limit the last two expansions.
FREQ=YEARLY to recur every year, BYMONTH to expand that to certain months in a year, and BYDAY and BYWEEKDAY to expand the BYMONTH rule even further.

VObject supports the EXDATE property for exclusions, but not yet the RDATE and EXRULE properties. If you're interested in this, please file a github issue, as this will put it on my radar.

This is a bit of a complex subject to go in excruciating detail. The RFC has a lot of examples though.

The hard part is not to write the RRULE, it is to expand them. The most complex and hard-to-read code is hidden in this component. Dragons be here.

So, if we have a meeting every 2nd monday of the month, this would be specified as such:

BEGIN:VCALENDAR
  VERSION:2.0
  BEGIN:VEVENT
    UID:1102c450-e0d7-11e1-9b23-0800200c9a66
    DTSTART:20120109T140000Z
    RRULE:FREQ=MONTHLY;BYDAY=MO;BYSETPOS=2
  END:VEVENT
END:VCALENDAR

Note that normally it's not allowed to indent the object like this, but it does make it easier to read. This is also the first time I added in a UID, which is required for all VEVENT, VTODO and VJOURNAL objects!

To figure out all the meetings for this year, we can use the following syntax:

use Sabre\VObject;

$calendar = VObject\Reader::read($data);
$calendar->expand(new DateTime('2012-01-01'), new DateTime('2012-12-31'));

What the expand method does, is look at its inner events, and expand the recurring rule. Our calendar now contains 12 events. The first will have its RRULE stripped, and every subsequent VEVENT has the correct meeting date and a RECURRENCE-ID set.

This results in something like this:

BEGIN:VCALENDAR
  VERSION:2.0
  BEGIN:VEVENT
    UID:1102c450-e0d7-11e1-9b23-0800200c9a66
    DTSTART:20120109T140000Z
  END:VEVENT
  BEGIN:VEVENT
    UID:1102c450-e0d7-11e1-9b23-0800200c9a66
    RECURRENCE-ID:20120213T140000Z
    DTSTART:20120213T140000Z
  END:VEVENT
  BEGIN:VEVENT
    UID:1102c450-e0d7-11e1-9b23-0800200c9a66
    RECURRENCE-ID:20120312T140000Z
    DTSTART:20120312T140000Z
  END:VEVENT
  ..etc..
END:VCALENDAR

To show the list of dates, we would do this as such:

foreach($calendar->VEVENT as $event) {
    echo $event->DTSTART->getDateTime()->format(\DateTime::ATOM);
}

In a recurring event, single instances can also be overriden. VObject also takes these into consideration. The reason we needed to specify a start and end-date, is because some recurrence rules can be 'never ending'.

You should make sure you pick a sane date-range. Because if you pick a 50 year time-range, for a daily recurring event; this would result in over 18K objects.

Free-busy report generation

Some calendaring software can make use of FREEBUSY reports to show when people are available.

You can automatically generate these reports from calendars using the FreeBusyGenerator.

Example based on our last event:


// We're giving it the calendar object. It's also possible to specify multiple objects,
// by setting them as an array.
//
// We must also specify a start and end date, because recurring events are expanded.
$fbGenerator = new VObject\FreeBusyGenerator(
    new DateTime('2012-01-01'),
    new DateTime('2012-12-31'),
    $calendar
);

// Grabbing the report
$freebusy = $fbGenerator->result();

// The freebusy report is another VCALENDAR object, so we can serialize it as usual:
echo $freebusy->serialize();

The output of this script will look like this:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Sabre//Sabre VObject 2.0//EN
CALSCALE:GREGORIAN
BEGIN:VFREEBUSY
DTSTART;VALUE=DATE-TIME:20111231T230000Z
DTEND;VALUE=DATE-TIME:20111231T230000Z
DTSTAMP;VALUE=DATE-TIME:20120808T131628Z
FREEBUSY;FBTYPE=BUSY:20120109T140000Z/20120109T140000Z
FREEBUSY;FBTYPE=BUSY:20120213T140000Z/20120213T140000Z
FREEBUSY;FBTYPE=BUSY:20120312T140000Z/20120312T140000Z
FREEBUSY;FBTYPE=BUSY:20120409T140000Z/20120409T140000Z
FREEBUSY;FBTYPE=BUSY:20120514T140000Z/20120514T140000Z
FREEBUSY;FBTYPE=BUSY:20120611T140000Z/20120611T140000Z
FREEBUSY;FBTYPE=BUSY:20120709T140000Z/20120709T140000Z
FREEBUSY;FBTYPE=BUSY:20120813T140000Z/20120813T140000Z
FREEBUSY;FBTYPE=BUSY:20120910T140000Z/20120910T140000Z
FREEBUSY;FBTYPE=BUSY:20121008T140000Z/20121008T140000Z
FREEBUSY;FBTYPE=BUSY:20121112T140000Z/20121112T140000Z
FREEBUSY;FBTYPE=BUSY:20121210T140000Z/20121210T140000Z
END:VFREEBUSY
END:VCALENDAR

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