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.
This function caches information about specific filenames, so you only need to call clearstatcache if you are performing multiple operations on the same filename and require the information about that particular file to not be cached.
Affected functions include stat, lstat, file_exists, is_writable, is_readable, is_executable, is_file, is_dir, is_link, filectime, fileatime, filemtime, fileinode, filegroup, fileowner, filesize, filetype, and fileperms.
Whether to also clear the realpath cache.
Clear the realpath cache for a specific filename only; only used if clear_realpath_cache is true.
No value is returned.