How to track a file change?

Question

PHP

Hello.
How to track a file change?
And if it has changed let me know.
Preferably php or js.
That is, I set the path to the file and that's it. Then the script works by itself?

Answer 1

php.net/manual/ru/function.filemtime.php

Answer 2

inotify, available for php and js. It will be easier to implement on js (socket-io, daemon)