Engine::getAjaxError

static function getAjaxError($errorMsg = null)
{
	$error = "unknown";
	if ($errorMsg !== null)
	{
		$error = $errorMsg;
	}
	elseif (self::$isBufferRestarted)
	{
		$error = "buffer_restarted";
	}
	elseif (!self::isEnabled())
	{
		$error = "not_enabled";
	}
	elseif (defined("BX_BUFFER_SHUTDOWN"))
	{
		$error = "php_shutdown";
	}
	elseif (!Page::getInstance()->isCacheable())
	{
		$error = "not_cacheable";
	}
	elseif (!self::$isCompositeInjected)
	{
		$error = "not_injected";
	}

	header("X-Bitrix-Composite: Ajax (error:".$error.")");
	self::sendRandHeader();

	$response = array(
		"error" => true,
		"reason" => $error,
	);

	return CUtil::PhpToJSObject($response);
}