Run shell commands with PHP?

[joeywhale]

Occasionally my media server goes down and I'm wondering if it's possible to start it remotely using php to check the port and if it's not running invoke cron (or some other way) to run a shell command. Is this possible because this is not a strong area for me. Here's the process I use with PuTTy.[*]login to shell[*]cd to source/red5/dist[*]screen[*]./red5.sh[*]CTRL-A then D to detach[*]logout