Fastagi caller AST server


For example I have 3 Asterisk server and these servers call One phpagi file via FASTAGI technology.

How could the phpagi detect who called (which Asterisk server) it?

The agi object doesn’t contain any information about it.
Of course I can use channel variables, but I would like to avoid it.
It’s important to know because the sound’s paths could be diferent each Asterisk server.