Untitled

<?php
if(isset($_SESSION['username'])) { header("Location: index.php"); }
session_start();
if(isset($_POST['submit'])){
    $Username = $db->real_escape_string($_POST['username']);
    $Password = $db->real_escape_string($_POST['password']);
    $CheckAcc = $db->query("SELECT id FROM users WHERE username = '$Username' AND password = '$Password' LIMIT 1");
    if($db->num_rows($CheckAcc))
    {
        $_SESSION['username'] = $Username;
        header("Location: index.php?p=index");
    } else {
        echo 'Die angegebenen Benutzerdaten, scheinen nicht korrekt zu sein!';
    }
}
?>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="description" content="">
    <meta name="author" content="">

    <title><?php echo $lang['w_title'];?> - Login</title>

    <!-- Bootstrap core CSS -->
    <link href="system/design/css/bootstrap.min.css" rel="stylesheet">

    <!-- Custom styles for this template -->
    <link href="system/design/css/signin.css" rel="stylesheet">

    <!-- Just for debugging purposes. Don't actually copy these 2 lines! -->
    <!--[if lt IE 9]><script src="../../assets/js/ie8-responsive-file-warning.js"></script><![endif]-->
    <script src="system/design/js/ie-emulation-modes-warning.js"></script>

    <!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
    <!--[if lt IE 9]>
      <script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
      <script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
    <![endif]-->
  </head>

  <body>

    <div class="container">

        <form class="form-signin" role="form" method="post">
        <h2 class="form-signin-heading">Bitte Einloggen</h2>
        <label for="inputtext" class="sr-only">Benutzername</label>
        <input type="text" id="inputEmail" class="form-control" placeholder="Benutzername" name="username" autofocus>
        <br>
        <label for="inputpassword" class="sr-only">Passwort</label>
        <input type="password" id="inputPassword" class="form-control" placeholder="Passwort" name="password">
        <div class="checkbox">
          <label>
                Noch nicht Registriert,dann <a href="index.php?p=register">hier</a> entlang.
          </label>
        </div>
        <button class="btn btn-lg btn-primary btn-block" type="submit" name="submit">Login</button>
      </form>

    </div> <!-- /container -->


    <!-- IE10 viewport hack for Surface/desktop Windows 8 bug -->
    <script src="system/design/js/ie10-viewport-bug-workaround.js"></script>
  </body>
</html>