[support] Cookie/Visit Tracking + Redirection

[lists at southernohio.net]

I have a situation where I need to push visitors back to a welcoming  
page if they've not visited the site previously.  I have implemented  
it in the drupal index.php page, however it doesn't seem to be  
reliably working so I wanted to post this for review, comments and  
suggestions as to the proper way to control this.  Perhaps there is  
even a module that I'm missing that would be better suited so please  
advise as you see fit:

index.php:
*** BEGIN PASTE ***
<?php
//... First Drupal Comments ...
// BEGIN OUR FUNCTIONS
// if they're new, send them back to the welcome page, else, check if  
they come from signup and set has_visited

$referring_url = $_SERVER['HTTP_REFERER'];    // get the referring  
URL, looking for http://www.mydomain.com/welcome/
$position_result = strpos($referring_url, "welcome");

if ( ($position_result > 0) || isset( $_COOKIE['has_visited'] ) ) {
	setcookie("has_visited", true, time()+7776000);
	}
else { 	
	header('Location:/welcome/index_main_site_entry.php');
	}

// END OUR FUNCTIONS

echo $_SESSION['HTTP_REFERER'];
//... rest of index.php ...
*** END PASTE ***

ALSO, in the index_main_site_entry.php file I would like to test to  
see if has_visited has been set so that I can pass them on into the  
site, but I've not been able to make that one work reliably at all.


Thanks in advance for your input!

-George