[SOLVED] $_SESSION question

[jmr3460]

I am trying to call a session value that was set on previous page. (Set_sessions.php)

<?php
ini_set ("display_errors", "1");
error_reporting(E_ALL);if ((empty($_POST['username'])) && (empty($_POST['password'])))
{
		header("Location: index.php");
		exit();
}
elseif ((!isset($_POST['username'])) && (!isset($_POST['password'])))
{
		header("Location: index.php");
		exit();
}
//testing for admin user
elseif ((isset($_POST['username'])) && (isset($_POST['password'])))
{
//id names of database and table to use
$db_name = "arscnaor_groupinfo";
//connect to server and select database
$connection = @mysql_connect("localhost", "user", "password")
     or die(mysql_error());
$db = @mysql_select_db($db_name, $connection) or die(mysql_error());

//build and issue ADMIN query
$sql = "SELECT * FROM admin WHERE
username = \"$_POST[username]\" AND
password = password(\"$_POST[password]\")";
$result = @mysql_query($sql) or die (mysql_error());

//get the number of rows in the result set
$num = mysql_numrows($result);
$id = mysql_fetch_array($result);
//set a cookie and print display if authorized,
//or redirect elsewhere if unauthorized
	if ($num != 0) {
		session_start();
		$_SESSION['admin_id'] = $id['id'];
	  $_SESSION['admin_user'] = $id['username'];
	  header("Location: admin_updates.php");
	  exit();
	   }
	   elseif ((isset($_POST['username'])) && (isset($_POST['password'])));
	   {
//build and issue GROUP query
$sql = "SELECT * FROM auth_users WHERE
username = \"$_POST[username]\" AND
password = password(\"$_POST[password]\")";

$result = @mysql_query($sql) or die (mysql_error());

//get the number of rows in the result set
$num = mysql_numrows($result);
$id = mysql_fetch_array($result);
//set a cookie and print display if authorized,
//or redirect elsewhere if unauthorized
	if ($num != 0) {
		session_start();
		$_SESSION['group_id'] = $id['id'];
	  $_SESSION['group_user'] = $id['username'];
	  header("Location: group_updates.php");
	  exit();
}
}
}
?>

I am directed to the proper pages. I think that my opening if statemant is rediredting me back to my index.php page and I do not know why. This is my php block:

<?php
ini_set ("display_errors", "1");
error_reporting(E_ALL);
if (!isset($_SESSION['admin_user']))
{
     header("Location: index.php");
     exit;
}
?>

This is my first Sessions script. I can echo session value from the session_set.php page. Why is it redirecting me back to the index page? I read this script to say "If $_SESSION['admin_user'] is not set then run the header(). I know the value is set I can echo it from the previous page. What am I missing?

[jmr3460]

Sorry I missed my 10 minute time limit. I found the problem on another post. I did not know that I need to session_start(); on every page. I learned something else today. Thanks for the views.