PHP ftp_site() Function

<?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);

// try to send SITE command
if (ftp_site($ftp_conn, "chmod 777 serverfile.txt"))
  {
  echo "Command executed successfully";
  }
else
  {
  echo "Command failed";
  }

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