(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
ftp_nb_fget — Retrieves a file from the FTP server and writes it to an open file (non-blocking)
$ftp,$stream,$remote_filename,$mode = FTP_BINARY,$offset = 0ftp_nb_fget() retrieves a remote file from the FTP server.
The difference between this function and ftp_fget() is that this function retrieves the file asynchronously, so your program can perform other operations while the file is being downloaded.
ftpAn FTP\Connection instance.
streamAn open file pointer in which we store the data.
remote_filenameThe remote file path.
mode
       The transfer mode. Must be either FTP_ASCII or
       FTP_BINARY.
      
offsetThe position in the remote file to start downloading from.
   Returns FTP_FAILED or FTP_FINISHED
   or FTP_MOREDATA.
  
| Version | Description | 
|---|---|
| 8.1.0 | The ftpparameter expects an FTP\Connection
  instance now; previously, a resource was expected. | 
| 7.3.0 | The modeparameter is now optional. Formerly it
       has been mandatory. | 
Example #1 ftp_nb_fget() example
<?php
// open some file for reading
$file = 'index.php';
$fp = fopen($file, 'w');
$ftp = ftp_connect($ftp_server);
$login_result = ftp_login($ftp, $ftp_user_name, $ftp_user_pass);
// Initiate the download
$ret = ftp_nb_fget($ftp, $fp, $file, FTP_BINARY);
while ($ret == FTP_MOREDATA) {
   // Do whatever you want
   echo ".";
   // Continue downloading...
   $ret = ftp_nb_continue($ftp);
}
if ($ret != FTP_FINISHED) {
   echo "There was an error downloading the file...";
   exit(1);
}
// close filepointer
fclose($fp);
?>