Returns TRUE if the
filename exists and is writable. The filename argument may be
a directory name allowing you to check if a directory is
writeable.
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.
The results of this function are cached. See
clearstatcache() for more details.
This function will not work on remote files; the file to be
examined must be accessible via the server's filesystem.
See also is_readable().