Returns the user ID of the owner of the file, or FALSE in case of an error. The user ID is returned in numerical format, use posix_getpwuid() to resolve it to a username.
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.