What is the likelihood of session_id on one PC matching with another PC?

The likelihood of session_id on one PC matching with another PC is extremely low due to the random and unique nature of session_ids generated by PHP. To further reduce the chances of session_id collision, you can use session_regenerate_id() function to generate a new session_id whenever a user logs in or changes privilege levels.

session_start();

// Regenerate session ID to prevent session fixation attacks
session_regenerate_id(true);