How do you run SSH from a PHP script?

I’m writing a very simple deployment script that logs into a remote server and uses Git to pull the latest code from the remote repository. The deployment application runs on Server A, and it will update code on Server B and Server C. The deployment application is written in PHP, and it’s easy enough to call the ssh command using PHP’s shell_exec() function. Well, calling SSH is easy, but making it work is a bit more difficult. SSH really wants to run as a user who has a .ssh directory in their home directory. First, it needs to find the private key in order to authenticate against the remote server. You can get around that using the -i flag and pointing at a specific key file. You also need to indicate to SSH that you don’t care about the host key (which prevents you from being victimized by man-in-the-middle attacks) or to point it to your known_hosts file. You can specify a custom location for that using the -o option, like this: -o UserKnownHostsFile=keys/known_hosts Even after that, though, SSH still insists on using a .ssh directory for the user running the command, in this case, the Apache user. Creating such a folder doesn’t seem like it should be necessary, but I haven’t been able to figure out how to avoid it. If I can’t get this to work, I could try using the SSH2 library for PHP, but I’d prefer not to, since I don’t want to deal with the added dependency. I’ve posted this question on Stack Overflow as well.