Custom PHP Scripts / AM_lite

I have a custom php call that works great in V3 based on product ids, but in the process of migrating to V4. Here is how it is set-up in V3 (obviously "mysite" is generic):


<?php session_start(); $user = $_SESSION['_amember_user']; if ($user['member_id'] > 0){
session_start(); $need_one_from = array(2,3,4,6,7,8);
if (array_intersect($need_one_from, $_SESSION['_amember_product_ids'])){
include("/home/mysite/public_html/mysite/php/subheaderpremium.php") ;
}
else {
include("/home/mysite/public_html/mysite/php/subheaderfree.php");
}}
else {
include("/home/mysite/public_html/mysite/php/subheader.php");
}
?>

I have tried calling the am_lite library and using the PAID and FREE constants, per the documentation in the manual at http://www.amember.com/docs/Content/PHPScripts but it just returns header errors. I am sort of at a loss here, any help is appreciated...