Simple Login System

index.php

<?php

require "session.php";

if(empty($_SESSION['loggedin']))
{
  include('templates/index.php');
  die();
}
else
{
  include('templates/login.php');
  die();
}

login.php

<?php

require "session.php";

if(!empty($_SESSION['loggedin'])
{
  header("Location: index.php");
}

if($_POST['username'] == 'admin' && $_POST['password'] = 'password')
{
  $_SESSION['loggedin'] = true;
  header("Location: index.php");
}
else
{
  include('template/login.php');
}

session.php

<?php

session_start();

//Put anything else here to be shared between all pages