Returns TRUE if the filename exists and is readable.
Keep in mind that PHP may be accessing the file as the user id that the web server runs as (often 'nobody'). Safe mode limitations are not taken into account.
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 L for a listing of which wrappers support stat() family of functionality.
See also is_writable(), file_exists(), and fgets().