Yes, PHP CAN do it provided on what you need to do.
Basically you can have PHP edit all your configs IF an d only if the user under which the web server is running has permissions to edit your config files (not a good idea). But if you set up a special apache web server only allowing access from localhost and which runs as root, you can practically have PHP do many sorts of neat things like start/stop processes, edit configs, etc -- Just like webmin.
But if you want to start/stop an apache server, think about this first: if the server stops, won't the PHP stop along with it too? So who's gonna turn on your server again?
You can get a lot of info provided you know where to look and whether you have permissions.
My suggestion to you, if you were going to create an "apache admin" program with PHP, set up another apache server which allows connections from only trusted hosts and runs as the root user. This was you can use this server to control other apache servers (the one running on port 80). This way you can stop and start your httpd server too.
About apache docs, sorry I don't know any helpful URLs. Maybe the apache website has links..... or try a mailing list.
-sridhar
