captcha-system | Code open-source permettant de créer un Captcha dans son | Bot library

There are several ways to handle this.

You could create a unique filename per user - that is per address and port using the $_SERVER['REMOTE_ADDR'] and $_SERVER['REMOTE_PORT'] variables to make a filename (possibly along with the time).

Note: port will change if socket is closed so if your client page isn't keeping a socket open over js, you will need to maintain a session id. The session ID would need to be generated server side and stored on the client side until the client is ready to return it along with the verification.

You could make php take out semaphors for each client.