Guys, what's the best practice to handle cross process communication? I

Question

Guys, what's the best practice to handle cross process communication? I

have a small service which depends on another executable binary helper process written in C++.
I need to pass input from php to that process, which should I use between the choices socket or exec
to handle this task?
exec(./process.exe arg_1).
If I use socket, I expected that process should be keep running all the time in server side in a single event while loop, it's ok. I just care about performance issue, which is better?