PHP Manual: is_dir
is_dir
Parameters
filenamePath to the file. If
filenameis a relative filename, it will be checked relative to the current working directory.
Notes
Note: The results of this function are cached. See clearstatcache() for more details.
Tip: As of PHP 5.0.0 this function can also be used with some URL wrappers. Refer to Appendix O for a listing of which wrappers support stat() family of functionality.