Session Not Working

Hello, I'm trying to use sessions for the first time. I have a log in script that gets the user to enter their name and password. Then the script compares the entered data to a database. If the entered data matches whats in the database then the user is granted access to the main php script. basically my code in the log in script is this: if ($user_data = = $database_data) { $_SESSION['verified_user']=1; header("Location:http://www.myserver.com/main.php"); exit; The opening code in my main.php script is this: session_start(); if ( isset($_SESSION['verified_user'])) { run the whole script }else { return to log in page exit; } Anyone care to clue me in as to why I'm always sent back to the log in page even when the log in is correct? Did I miss the session boat all together? Perhaps I'm not grasping it at all.. Thanks, Roger