Request::isAdminSection

public function isAdminSection()
{
	$requestedDir = $this->getRequestedPageDirectory();
	return (mb_substr($requestedDir, 0, mb_strlen("/bitrix/admin/")) == "/bitrix/admin/"
		|| mb_substr($requestedDir, 0, mb_strlen("/bitrix/updates/")) == "/bitrix/updates/"
		|| (defined("ADMIN_SECTION") && ADMIN_SECTION == true)
		|| (defined("BX_PUBLIC_TOOLS") && BX_PUBLIC_TOOLS === true)
	);
}