WebDAV Sync

Since version 1.9.0alpha1, sabre/dav comes with support for WebDAV Sync. WebDAV Sync provides a way for webdav servers to track what has been changed, and send the list of changes back to client.

WebDAV-Sync has been implemented by almost every Cal- and CardDAV client, and it has the ability to greatly reduce the number of HTTP requests needed, and reduces memory usage, cpu and bandwidth on the sabredav server. It's very much worth it to implement for these reasons alone.

The standard CalDAV and CardDAV PDO backends already provide support for this, and therefore, all you need to do to enable this, is to add the plugin to your server:

$server->addPlugin(
    new Sabre\DAV\Sync\Plugin()
);

CalDAV and CardDAV custom backends

If you created your own custom backend, you will need to add a few more methods to allow webdav-sync support to work.

To enable sync, your own backend class must implement the Sabre\CalDAV\Backend\SyncSupport interface, or for CardDAV Sabre\CardDAV\Backend\SyncSupport.

A lot of documentation on how to do this can be found in the actual interfaces. It's best to simply read the documentation there:

• CalDAV Backend SyncSupport documentation
• CardDAV Backend SyncSupport documentation

What it comes down to is this:

For every change, that is, an addition, deletion or modification of a calendar object, a vcard, a calendar or an addressbook, you must track this change and store it somewhere.

When clients use webdav sync, they will start by receiving a token. The next time a client syncs, it will provide this token and ask the server to request all changes since that token was issued.

Adding Sync support to your other collections

It is possible to add sync support to any custom collection. To do so, make sure your collection implements the Sabre\DAV\Sync\ISyncCollection interface.

This interface only requires two new methods. It's also here best to just read the in-line documentation as it's quite complete.