streamWrapper::stream_flush

This method is called in response to fflush() and when the stream is being closed while any unflushed data has been written to it before.

If you have cached data in your stream but not yet stored it into the underlying storage, you should do so now.

Should return TRUE if the cached data was successfully stored (or if there was no data to store), or FALSE if the data could not be stored.

If not implemented, FALSE is assumed as the return value.

fflush() -