The PHP ftp_rename() function renames a file or directory on the FTP server.

<?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);

$old_file = 'old-file.txt';
$new_file = 'new-file.txt';

// rename the file
if (ftp_rename($ftp_conn, $old_file, $new_file)) {
    echo 'The file was renamed successfully';
}
else {
    echo 'There was a problem renaming the file';
}

// close connection
ftp_close($ftp_conn);
?>

// renames the file on the FTP server

ftp_rename(ftp_conn, oldname, newname)