(PECL inotify >= 0.1.2)
inotify_add_watch — Add a watch to an initialized inotify instance
$inotify_instance
   , string $pathname
   , int $mask
   )
   inotify_add_watch() adds a new watch or modify an
   existing watch for the file or directory specified in
   pathname.
  
   Using inotify_add_watch() on a watched object replaces
   the existing watch. Using the IN_MASK_ADD constant
   adds (OR) events to the existing watch.
  
inotify_instanceResource returned by inotify_init()
pathnameFile or directory to watch
maskEvents to watch for. See Predefined Constants.
The return value is a unique (inotify instance wide) watch descriptor.