I'll be recompiling PHP this afternoon to add a needed module, and Apache (the web server) will need to be rebooted after that's done. The version will not change and any modules that are currently there will stay that way, I'm just adding one that's needed for the helpdesk ticket system.
In all likelihood none of this will be noticed, but if you happen to hit the server at just the right time as it's rebooting, the page may temporarily time out. It only takes the server a few minutes to recover from a reboot, and most web hosts never tell you before a server reboot, but we try to keep clients and users as informed as possible.
The entire process should take no more than 30 minutes (the server reboot less than 5), and when it's done I'll update this post.