The server script would run continuously.
Other scripts are normal websites, that should be able to communicate with the server script.
I've come across Ratchet (https://github.com/cboden/Ratchet), tried the example from here: http://socketo.me/docs/hello-world and it works :D
But the client needs javascript. And I would like to send the request to the server with PHP because the messages are linux commands, and I wouldn't want site visitors to be able to send linux commands to my server script. Also, only messages from scripts from "localhost" should be taken into consideration.
Is it possible to do this with Ratchet? Or are there other solutions for this?