<?php
// connect and login to FTP server
$ftp_server = 'ftp.example.com';

$ftp_conn = ftp_connect($ftp_server) or die('Could not connect to ' . $ftp_server);
$login = ftp_login($ftp_conn, $ftp_username, $ftp_userpass);

$server_file = 'server-file.txt';

// open file
$local-file = 'local-file.txt';
$fp = fopen($file, 'r');

// initiate download
$d = ftp_nb_fput($ftp_conn, $server_file, $fp, FTP_BINARY);

while ($d == FTP_MOREDATA) {
    // do something
  
    // continue downloading
    $d = ftp_nb_continue($ftp_conn);
}

if ($d != FTP_FINISHED) {
    echo 'Error downloading file';
    exit(1);
}

// close connection and file handler
ftp_close($ftp_conn);
fclose($fp);
?>