Know who installed your script

Hi, I want to find out who installed my scripts on their servers. Is there any tutorials for this? I think they're called callhomes? Thanks

plz give some more details

I'm guessing your script would either have a "ping" function put in, or
a "sendmail" to send an email to you. In either case, anyone with some
PHP knowledge would be able to spot that and shut it off. If you put that
into scripts that people actually paid for, they probably would be a bit
upset if they found out. This would essentially cost them extra bandwidth.

I've seen a tutorial like this but I can't find it anymore. It sends a "ping" style when they're in the process of installing it.