int ftp_nb_put ( resource $ftp_stream , string $remote_file , string $local_file , int $mode [, int $startpos = 0 ] )
ftp_nb_put() stores a local file on the FTP server. The difference between this function and the ftp_put() is that this function uploads the file asynchronously, so your program can perform other operations while the file is being uploaded.
Returns FTP_FAILED or FTP_FINISHED or FTP_MOREDATA.