"Require_Once" Help Please

[eluser]razerone[/eluser]
I am getting this error

Parse error: syntax error, unexpected '{' in /home/cws01/public_html/index.php on line 5

Code:

require_once('application/modules/install/installed');

if(!defined('INSTALLED') { <-- Error

require_once('application/modules/install');

}

installed.php application / install / controllers / installed.php

Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Installed extends MX_Controller {

function installed() {
  
  define('INSTALLED', true);
}

}