I a doing 4 ways traffic light project and it is working fine. I want to control it through a webpage. How How can I use a button on a webpage (software button) to interrupt the loop
What do you mean by “interrupt the loop”?
First, learn how to create a web server with a button. We have several examples you can use. Check the examples with buttons on the “Build Web Servers” eBook.
Then, on the loop(), you just need to check the state of the button on the loop() and do different tasks depending on the state of the button.