logout.php

<?php
// Initialize the session.
// If you are using session_name("something"), don't forget it now!
session_start();

// Unset all of the session variables.
$_SESSION = array();

// If it's desired to kill the session, also delete the session cookie.
// Note: This will destroy the session, and not just the session data!
if (ini_get("session.use_cookies")) {
    $params = session_get_cookie_params();
    setcookie(session_name(), '', time() - 42000,
        $params["path"], $params["domain"],
        $params["secure"], $params["httponly"]
    );
}

// Finally, destroy the session.
session_destroy();
?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
  <title>Fragen & Antworten | Registrieren</title>              
	<link href="style.css" type="text/css" rel="stylesheet">
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<meta name="description" content="Fragen und Antworten, Der Dozent stellt Fragen, die Studenten antworten." />
	<meta name="keywords" content="Fragen, Antworten, Quiz, Auswertung, BA-Glauchau" />
	<meta name="language" content="de, at" />
  </head>  
  <body>
  <div id="login">
	<?php
		if (isset($_SESSION['userid']))
		{
			$statement = mysqli_query($db, "SELECT * FROM users WHERE id=".$_SESSION['userid']."");
			$row = mysqli_fetch_object($statement);
			echo "Sie sind eingeloggt als <a class='Menuelink' href='main.php'>".$row->username."</a> | <a class='Menuelink' href='logout.php'>Ausloggen</a>";
		}
		else
		{
			echo "<a class='Menuelink' href='login.php'>Einloggen</a> | <a class='Menuelink' href='register.php'>Registrieren</a>";
		}	
	?>
  </div>
  <center> 
  <div id="header">
	<a class='Headerlink' href="main.php">
		Fragen und Antworten
	</a>
  </div>
  <div id="main">
	<br>Sie haben sich erfolgreich ausgeloggt.
  </div>
</body>
</html>