CDavGroupdavHandler::GetEntry

public function GetEntry($method, $id, $collectionId)
{
	$entry = $this->Read($collectionId, $id);

	if (!$entry && ($method != 'PUT' || $entry === false))
		return ($entry === false) ? '403 Forbidden' : '404 Not Found';

	$minimumPrivilege = $this->GetMethodMinimumPrivilege($method);
	$request = $this->groupdav->GetRequest();
	if (!$this->CheckPrivileges($minimumPrivilege, $request->GetPrincipal(), $collectionId))
		return '403 Forbidden';

	if ($entry)
	{
		$etag = $this->GetETag($collectionId, $entry);

		// If the clients sends an "If-Match" header ($_SERVER['HTTP_IF_MATCH']) we check with the current etag
		// of the calendar --> on failure we return 412 Precondition failed, to not overwrite the modifications
		if ($request->GetParameter('HTTP_IF_MATCH') !== null)
		{
			$m = $request->GetParameter('HTTP_IF_MATCH');
			if (mb_strstr($m, $etag) === false)
			{
				$this->httpIfMatch = $m;
				return '412 Precondition Failed';
			}
			else
			{
				$this->httpIfMatch = $etag;
				// if an IF_NONE_MATCH is given, check if we need to send a new export, or the current one is still up-to-date
				if ($method == 'GET' &&	$request->GetParameter('HTTP_IF_NONE_MATCH') !== null)
					return '304 Not Modified';
			}
		}

		// Workaround for Mac OS X Lion > 10.7.3
		// if ($request->GetParameter('HTTP_IF_NONE_MATCH') !== null)
		// {
			// $m = $request->GetParameter('HTTP_IF_NONE_MATCH');
			// if (strstr($m, $etag) !== false || $m == '*')
			// {
				// Do nothing!
				// Mac OS X Lion > 10.7.3 is sending a one more request after event creating or modifying.
				// If we will return 304, iCal will always create new events with title "New event"
				//return '304 Not Modified';
			// }
			// else
			// {
				//return '412 Precondition Failed';
			// }
		// }
	}

	return $entry;
}