a file_get_contents call via a php script ... triggered by a client-user running the php page.. will not show any footprints from the client.
server a hosts page a.
server b hosts page b.
page a does a file_get_contents to snag page b from server b.
user c goes to page a on server a.
page a gets the contents of page b.
server b will get footprint info from server a, since server a is the content getter. essentially, in this relationship, server a is the client of server b's page. also, with curl, these variables can all be hacked, so from server b's perspective (the one which you are asking about), the only reliable data is the IP of where the request is coming from. that can be done through a proxy so it doesn't lead back to server a. IP can be spoofed, but it is pointless, because the data from the file_get_contents or curl call would be sent to the spoofed IP, not to the spoofer.
you can lock down your content if you are concerned about screen scrapes and vultures through a combination of various methods (HTTACCESS etc).
