PHP拒绝接受cookie

When I develop web page Faced a problem which happen when use session

<?php
session_start();
ob_start();
    if ($type == 'admin') {
                $_SESSION['user_name'] = $User;
                $_SESSION['UserType'] = 'admin';
                header('Location: Main.php');
            } else if ($type == 'manager' && $PID != "") {
                $_SESSION['user_name'] = $User;
                $_SESSION['UserType'] = 'manager';
                $_SESSION['PID'] = $PID;
                header('Location: MainPage.php');
            }
?>

this Error in all my cases:

"Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

This problem can sometimes be caused by disabling or refusing to accept cookies."

Your script looks like that youre redirecting in a circle. Main.php-> main.php -> main.php and so on. Check your script for such a mistake