(PECL eio >= 0.0.1dev)
eio_fstatvfs — Get file system statistics
   eio_fstatvfs() returns file system statistics in
  result of callback.
  
fd
    A file descriptor of a file within the mounted file system.
pri
    The request priority: EIO_PRI_DEFAULT, EIO_PRI_MIN, EIO_PRI_MAX, or NULL.
If NULL passed, pri internally is set to
EIO_PRI_DEFAULT.
callback
    
callback function is called when the request is done.
It should match the following prototype: 
void callback(mixed $data, int $result[, resource $req]);
data
is custom data passed to the request.
result
request-specific result value; basically, the value returned by corresponding system call.
req
is optional request resource which can be used with functions like eio_get_last_error()
data
    
     Arbitrary variable passed to callback.
     
    eio_fstatvfs() returns request resource on success or FALSE on error.