CTaskSync::UpdateItem

static function UpdateItem($arFields, $arTask)
{
	global $DB;

	// do not call static::checkExchangeAvailable() untill you sure exchange is needed for the task, or else you`ll load the module with no purpose

	$isResponsibleChanged = isset($arFields['RESPONSIBLE_ID'])
		&& isset($arTask['RESPONSIBLE_ID'])
		&& ((int)$arFields['RESPONSIBLE_ID'] !== (int)$arTask['RESPONSIBLE_ID']);

	// If responsible changed, we must reassign task to other Exchange-account,
	// but not update the existing task in account of prev. responsible
	if ($isResponsibleChanged && static::checkExchangeAvailable())
	{
		// Prevent unexpected resynchronization of this task in case if DeleteItem() or AddItem() will not complete they work
		$strSql = "UPDATE b_tasks SET EXCHANGE_ID = NULL, EXCHANGE_MODIFIED = NULL WHERE ID = " . (int) $arTask['ID'];
		$DB->Query($strSql, false, "File: ".__FILE__."
Line: ".__LINE__);

		self::DeleteItem($arTask);
		$arActualTaskData = array_merge($arTask, $arFields);
		self::AddItem($arActualTaskData);

		return;
	}

	// If item is not in Exchange, skip it ...
	if ( ! ($arTask["EXCHANGE_ID"] && $arTask["EXCHANGE_MODIFIED"]) )
	{
		// ... but if there is responsible changed - create task in Exchange
		if ($isResponsibleChanged && static::checkExchangeAvailable())
		{
			$arActualTaskData = array_merge($arTask, $arFields);
			self::AddItem($arActualTaskData);
		}

		return;
	}

	if(!static::checkExchangeAvailable())
	{
		return;
	}

	$bodyType = 'html';

	if (isset($arFields['DESCRIPTION_IN_BBCODE']))
	{
		if ($arFields['DESCRIPTION_IN_BBCODE'] === 'Y')
			$bodyType = 'text';
	}

	$priorityMapping = array_flip(self::$PriorityMapping);
	$arModifyEventArray = array(
		"USER_ID" => $arFields["RESPONSIBLE_ID"] ? $arFields["RESPONSIBLE_ID"] : $arTask["RESPONSIBLE_ID"],
		"BODY_TYPE" => $bodyType
	);
	if ($arFields["TITLE"])
	{
		$arModifyEventArray["SUBJECT"] = $arFields["TITLE"];
	}
	if ($arFields["DESCRIPTION"])
	{
		$arModifyEventArray["BODY"] = $arFields["DESCRIPTION"];
	}
	if ($arFields["PRIORITY"])
	{
		$arModifyEventArray["IMPORTANCE"] = $priorityMapping[mb_strtolower($arFields["PRIORITY"])];
	}

	if (isset($arFields['GUID']))
		$arModifyEventArray['GUID'] = $arFields['GUID'];

	//$arModifyEventArray['SERIALIZED_DATA'] = serialize($arFields);

	if ($arFields["DURATION_FACT"])
	{
		$arModifyEventArray["ACTUAL_WORK"] = $arFields["DURATION_FACT"] * 60;
	}
	if ($arFields["START_DATE_PLAN"])
	{
		$arModifyEventArray["START_DATE"] = $arFields["START_DATE_PLAN"];
	}
	if ($arFields["DEADLINE"])
	{
		$arModifyEventArray["DUE_DATE"] = $arFields["DEADLINE"];
	}
	if ($arFields["STATUS"])
	{
		$arModifyEventArray["STATUS"] = self::$StatusMappingReverse[$arFields["STATUS"]];
	}
	if ($arFields["DURATION_PLAN"])
	{
		$arModifyEventArray["TOTAL_WORK"] = $arFields["DURATION_PLAN"] * 60;
	}

	$result = CDavExchangeTasks::DoUpdateItem($arModifyEventArray["USER_ID"], $arTask["EXCHANGE_ID"], $arTask["EXCHANGE_MODIFIED"], $arModifyEventArray);

	if (array_key_exists("XML_ID", $result))
	{
		$arExchangeFields = array(
			"EXCHANGE_MODIFIED" => $result["MODIFICATION_LABEL"]
		);
		$strUpdate = $DB->PrepareUpdate("b_tasks", $arExchangeFields, "tasks");
		$strSql = "UPDATE b_tasks SET ".$strUpdate." WHERE ID=".$arFields["ID"];
		$DB->Query($strSql, false, "File: ".__FILE__."
Line: ".__LINE__);
	}
}