PHP returning "undefined" variable to flash - php

Question

I don't know what's wrong but the moment i've logged in, i wanted it to display hello + username that i log in with. But currently it only displays Helloundefined
This is my flash code:
var myurl2:String = "http://localhost:8888/storyboards/check_auth.php";
var scriptLoader2:URLLoader = new URLLoader();
var scriptRequest2:URLRequest = new URLRequest();
scriptRequest2.url = myurl2+"?ck=" + new Date().getTime();
scriptLoader2.addEventListener(Event.COMPLETE, handleLoadSuccess2);
scriptLoader2.addEventListener(IOErrorEvent.IO_ERROR, handleError2);
// turn off right click so that user cannot control the movie
stage.showDefaultContextMenu = false;
scriptRequest2.method = URLRequestMethod.POST;
scriptLoader2.load(scriptRequest2);
function handleLoadSuccess2(evt:Event):void
{
var variables2:URLVariables = new URLVariables( evt.target.data );
for (var prop in variables2) {
trace(prop+" is: "+variables2[prop]);
}
if (variables2.authenticated == "y") {
// if login details OK, load protected page
nextFrame();
display_txt.text ="Hello" + variables2.username;
} else {
// if login details OK, load protected page
var url:String = "http://localhost:8888/storyboards/login.html";
var request2:URLRequest = new URLRequest(url);
try {
navigateToURL(request2, '_self'); // second argument is target
} catch (e:Error) {
trace("Error occurred!");
}
}
}
function handleError2(evt:IOErrorEvent):void
{
}
stop();
//------------------and here's my php code for process_login.php----------------------//
<?php
$host = 'localhost';
$user = 'root';
$password = 'root';
// check correct variables have been received through the POST array
if (isset($_POST['username']) && isset($_POST['pwd'])){
session_start();
// base url
$baseURL = 'http://localhost:8888/storyboards/';
// include info for db connection
//require_once("connection.php");
// escape quotes
if (!get_magic_quotes_gpc()) {
foreach($_POST as $key => $value) {
$temp = addslashes($value);
$_POST[$key] = $temp;
}
}
// connect to mysql
$connection = mysql_connect($host, $user, $password) ;
if (!$connection) {
echo '&error=' . mysql_error() . '&';
die('Could not connect ' . mysql_error());
}
//echo 'Connected successfully.';
// connect to db
$database = 'registerform';
$db = mysql_select_db($database, $connection);
if (!$db) {
echo '&error=' . mysql_error() . '&';
die ('Not connected : ' . mysql_error());
}
//echo 'Selected successfully.';
// query
$query = 'SELECT user_name, pwd FROM users WHERE user_name = "' . $_POST['username'] . '" AND pwd = "' . sha1($_POST['pwd']) . '"';
$result = mysql_query($query, $connection);
if (!$result) {
echo '&error=' . mysql_error() . '&';
die ('Invalid query: ' . mysql_error());
}
// count the number of records
$numrows = mysql_num_rows($result);
if ($numrows > 0) {
$_SESSION['authenticated'] = $_POST['username'];
echo 'authenticated=y' . '&page=' .'pass.php&user_name='.$_SESSION['authenticated'];
} else {
echo 'authenticated=n&error=' . urlencode('Sorry, access denied.');
}
}
?>
//-----------and my php code for check_auth.php----//
<?php
// access to the current session
session_start();
$_SESSION['username'] = $_POST['username'];
// if session variable authenticated is not set
if (!isset($_SESSION['authenticated'])) {
echo 'authenticated=n';
} else {
echo 'authenticated=y';
}
?>
Is there anywhere in the above codes that I went wrong? Can someone out there pls help me :(