I am looking to get a server at softlayer. I want to be able to send ssh commands from my web server to this new softlayer server. For security purposes I would like to disable the ssh completely on the public port and access it through the private network.

If I get hosting with a company that is also in softlayer, I would already have access to the private network, correct? Therefore I could just have the php script execute with the private address as the destination.

If I host with a company outside of softlayer, I believe I would need a script to connect to the softlayer VPN first, correct? Does anyone know of php script that would do this?

What you want to do is possible if softlayer provides you an internal ip address such as 192.168.xxx.xxx, 172.16.xxx.xxx 10.xxx.xxx.xxx...

You would need to have sshd listen on that particular IP address, example:

ListenAddress 10.0.1.10

I would however recommend doing it a different way. I would bind sshd to an external address, limit user, disable root logins, and use a key... You don't want to be locked out of two boxes if one goes down...

I don't think php will be of any use to you when it comes to vpn unless you're using it to exec system commands and pretty much any language can do that...