Warning: ftp_get(): RETR

I am using this code:

   <?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);

$local_file = "local.zip";
$server_file = "server.zip";

// download server file
if (ftp_get($ftp_conn, $local_file, $server_file, FTP_ASCII))
  {
  echo "Successfully written to $local_file.";
  }
else
  {
  echo "Error downloading $server_file.";
  }

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

In order to get a specific file from a server. I tried also using -

if (ftp_get($ftp_conn, $local_file, $server_file, FTP_BINARY))

insted of

if (ftp_get($ftp_conn, $local_file, $server_file, FTP_ASCII))

I kepp getting the error- Warning: ftp_get(): RETR in myfile.php on line 13.

Please Help.