Note that this function affects only file metadata. However, all the PHP file system functions do their own caching of actual file contents as well. You can use the "realpath_cache_size = 0" directive in PHP.ini to disable the content caching if you like. The default content caching timeout is 120 seconds.
Content caching is not a good idea during development work and for certain kinds of applications, since your code may read in old data from a file whose contents you have just changed.
Note: This is separate from the caching typically done by browsers for all GET requests (the majority of Web accesses) unless the HTTP headers override it. It is also separate from optional Apache server caching.
