Security Assist issues

Hello,

I'm having some issues with Security Assist.

The first problem is when I add :
<?php
if (!isset($_SESSION)) {
session_start();
}
?>
on top of my page, I get the following warning message :

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /public_html/gainde/welcome.php:1) in /public_html/gainde/welcome.php on line 3

The second issue is that, if the page's name is index.php and I add a dynamic text (i.e: {WAATKmembre.MemPseudo}) on it, I cannot see it even if I'm logged in. But if I change the page name to something else (i.e: welcome.php, home.php...), I can see the dynamic text.

I have attached the security assist and the index.php files for your references.

Thanks in advance for your help.