query("SELECT COUNT(*) FROM students WHERE mnumber = $mnumber")->fetch(PDO::FETCH_NUM)[0] == 1) {
    print "
";
      print "| user already registered | 
|---|
";
    print "
";
    exit;
  }
  $db->query("INSERT INTO students (mnumber,firstname,lastname,email,password) 
        VALUES (\"$mnumber\",\"$firstname\",\"$lastname\",\"$email\",\"$password\")");
  print "";
    print "| registration successfull | 
|---|
";
  print "
";
  echo "$firstname $lastname was successfully registered.
";
  // send password-email //
  $nachricht = "Hello $firstname($mnumber)!\nYou registered for " . $PREFS['exname'] . " (" . $PREFS['groupname'] . ").\nRemember your password: $password\n\nYours,\nBanana.";
  $empfaenger = 'niemand@example.com';
  $betreff = 'Der Betreff';
  $header = 'From: banana@treefish.org' . "\r\n" .
    'Reply-To: noreply@treefish.org' . "\r\n" .
    'X-Mailer: PHP/' . phpversion();
  mail($email, "Banana Registration: " . $PREFS['exname'] . " (" . $PREFS['groupname'] . ")", $nachricht, $header);
  exit;
}
?>