I just read this:
opcache.validate_timestamps - When this is enabled, PHP will check the file timestamp per your opcache.revalidate_freq value.
When it’s disabled, opcache.revaliate_freq is ignored and PHP files are NEVER checked for updated code. So, if you modify your code, the changes won’t actually run until you restart or reload PHP (you force a reload with kill -SIGUSR2).
Yes, this is a pain in the ass, but you should use it. Why? While you’re updating or deplying code, new code files can get mixed with old ones— the results are unknown. It’s unsafe as hell.