LiviutzuAs on "Undefined Function gives me WHITE PAGE"

I get this error in error_log:

[18-Sep-2013 15:13:32 Europe/Bucharest] PHP Fatal error: Call to undefined function define() in /home/traimuzi/public_html/index.php on line 14

When this error appears, front-end ( visitors view ) is a blank page.

I don`t understand why!

Here is the index.php code:

<?php
/**
 * Front to the WordPress application. This file doesn't do anything, but loads
 * wp-blog-header.php which does and tells WordPress to load the theme.
 *
 * @package WordPress
 */

/**
 * Tells WordPress to load the WordPress theme and output it.
 *
 * @var bool
 */
define('WP_USE_THEMES', true);

/** Loads the WordPress Environment and Template */
require('./wp-blog-header.php');

Here is the website: Traieste Muzica