This page is not redirecting properly - php

Question

I used the following script from about.com: http://php.about.com/od/finishedphp1/ss/php_login_code_2.htm
The problem is that a few times it gives me this error: The page isn't redirecting properly. Firefox has detected that the server is redirecting the request for this address in a way that will never complete.
Code:
<?php
session_start();
// Process the POST variables
$username = $_SESSION["user_name"];
//$password = $_POST["password"];
// Set up the session variables
$_SESSION["user_name"] = $username;
$ugh = $_REQUEST['url_name'];
if($_POST){
$_SESSION['user_name']=$_POST["user_name"];
$_SESSION['password']=$_POST["password"];
}
$secret = $info['password'];
//Checks if there is a login cookie
if(isset($_COOKIE['ID_my_site']))
//if there is, it logs you in and directes you to the members page
{
$username = $_COOKIE['ID_my_site'];
$pass = $_COOKIE['Key_my_site'];
$check = mysql_query("SELECT user_name, password
FROM users WHERE user_name = '$username'
and url_name='$ugh'")or die(mysql_error());
while($info = mysql_fetch_array( $check ))
{
if (# $info['password'] != $pass)
{
}
else
{
header("Location: home.php");
}
}
}
//if the login form is submitted
if (isset($_POST['submit'])) { // if form has been submitted
// makes sure they filled it in
if(!$_POST['user_name'] | !$_POST['password']) {
die('You did not fill in a required field.');
}
// checks it against the database
if (!get_magic_quotes_gpc()) {
$_POST['user_name'] = addslashes($_POST['user_name']);
}
$check = mysql_query("SELECT user_name,password
FROM users WHERE user_name = '".$_POST['user_name']."'
and url_name='".$ugh."'")or die(mysql_error());
//Gives error if user dosen't exist
$check2 = mysql_num_rows($check);
if ($check2 == 0) {
die('That user does not exist in our database.
<a href=add.php>Click Here to Register</a>');
}
while($info = mysql_fetch_array( $check ))
{
$_POST['password'] = md5($_POST['password']);
$_POST['password'] = $_POST['password'];
//gives error if the password is wrong
if (# $_POST['password'] != $info['password']) {
die('Incorrect password, please try again');
}
else
{
// if login is ok then we add a cookie
$_POST['user_name'] = stripslashes($_POST['user_name']);
$hour = time() + 3600;
setcookie(ID_my_site, $_POST['user_name'], $hour);
setcookie(Key_my_site, $_POST['password'], $hour);
//then redirect them to the members area
header("Location: home.php");
}
}
}
else
{
// if they are not logged in
?>
2nd code:
Then on each member page i use the following to make sure their login is correct:
// Process the POST variables
$email = $_SESSION["user_name"];
// Set up the session variables
$_SESSION["user_name"] = $username;
if(!isset($_SESSION['user_name'])) { header("Location: log.php");}

Answer 1

To paraphrase Blowski: http://kb.mozillazine.org/The_page_is_not_redirecting_properly
It's like firefox has reached it's maximum recursion depth: it has detected a seemingly endless loop of redirects

Answer 2

What's the name of the files in the above scripts? If the name of the first script is home.php, then when a user visits home.php, it will keep reloading if the password is incorrect, so Firefox will return that message.
Alternatively, do you have anything in your .htaccess which is causing it?