Yeah the current block chain is around 100GB. Well with port forwarding you could let the server connect to your mac (through your public ip) OR through a reverse SSH tunnel (I'd prefer this because you wouldn't need to open a port on your pc). but your mac would have to run all the time it's needed. Also I'm sure you can set ip white list in the config files (for more security). Then for PHP I don't know I've never used any like that but I'm sure you could find some.