The clearstatcache() function clears the file status cache. PHP caches data for some functions for better performance. If a file is being checked several times in a script, you might want to avoid caching to get correct results. To do this, use the clearstatcache() function.
void clearstatcache ([ bool $clear_realpath_cache = FALSE [, string $filename ]] )
When you use stat(), lstat(), or any of the other functions listed in the affected functions list (below), PHP caches the information those functions return in order to provide faster performance. However, in certain cases, you may want to clear the cached information. For instance, if the same file is being checked multiple times within a single script, and that file is in danger of being removed or changed during that script's operation, you may elect to clear the status cache. In these cases, you can use the clearstatcache() function to clear the information that PHP caches about a file.
You should also note that PHP doesn't cache information about non-existent files. So, if you call file_exists() on a file that doesn't exist, it will return FALSE until you create the file. If you create the file, it will return TRUE even if you then delete the file. However unlink() clears the cache automatically.
The above example will output something similar to:
Functions that are caching: