从另一个ftp服务器下载csv文件并进行修改

Question

我的ftp凭据是正确的。我在一台服务器上传的PHP代码让我们说example.com，在这台服务器上我试图下载example2.com上的csv文件。虽然下载时显示问题。

<?php
$ftp_server = "ftp.example.com";

$remote_file = 'amit.csv';
$local_file = 'amit2.csv';

// open some file to write to
$handle = fopen($local_file, 'w');

// set up basic connection
$conn_id = ftp_connect($ftp_server);

// login with username and password
$login_result = ftp_login($conn_id, 'user@example2.com', 'mypassword');

// try to download $remote_file and save it to $handle
if (ftp_fget($conn_id, $handle, $remote_file, FTP_ASCII, 0)) {
 echo "successfully written to $local_file\n";
} else {
 echo "There was a problem while downloading $remote_file to $local_file\n";
}

// close the connection and the file handler
ftp_close($conn_id);
fclose($handle);
?> 

我想下载/读取amit.csv，进行一些修改并上传到另一台服务器example3.com。我应该怎么做呢？