public function has(string $serviceId): bool
    {
        return isset(self::$services[$serviceId]) || isset(self::$aliases[$serviceId]);
    }
public function has(string $serviceId): bool
    {
        return isset(self::$services[$serviceId]) || isset(self::$aliases[$serviceId]);
    }
public function has ( string $ serviceId ) : bool { return isset ( self :: $ services [ $ serviceId ] ) || isset ( self :: $ aliases [ $ serviceId ] ) ; }
Check whether a given service exists.

@param string $serviceId The service

@return bool
Check whether a given service exists .