User::isAdmin

public function isAdmin()
{
	try
	{
		if(ModuleManager::isModuleInstalled('bitrix24') && Loader::includeModule('bitrix24'))
		{
			return CBitrix24::isPortalAdmin($this->getId());
		}

		global $USER;

		if($USER instanceof CUser && $this->getId() === $USER->getId())
		{
			return $USER->isAdmin();
		}

		$user = new CUser();

		return in_array(1, $user->getUserGroup($this->getId()));
	}
	catch(Exception $e)
	{}

	return false;
}