Ошибка Undefined variable '$steamauth' что исправить

<?php
ob_start();
session_start();

function logoutbutton() {
echo "<form action='' method='get'><button name='logout' type='submit'>Logout</button></form>"; //logout button
}

function loginbutton($buttonstyle = "square") {
$button['rectangle'] = "01";
$button['square'] = "02";
//$button = "<a href='?login'><img src='https://steamcommunity-a.akamaihd.net/public/images/signinthroughsteam/sits_".$button[$buttonstyle].".png'></a>";
$button = "<a href='?login' class='main_header_login_link'><img src='login.png'></a>";

echo $button;
}


if (isset($_GET['login'])){
require 'openid.php';
try {

require 'SteamConfig.php';
$openid = new LightOpenID($steamauth['domainname']);



if(!$openid->mode) {
$openid->identity = ' https://steamcommunity.com/openid ';
header('Location: ' . $openid->authUrl());
} elseif ($openid->mode == 'cancel') {
echo 'User has canceled authentication!';
} else {
if($openid->validate()) {
$id = $openid->identity;
$ptn = "/^https?:\/\/steamcommunity\.com\/openid\/id\/(7[0-9]{15,25}+)$/";
preg_match($ptn, $id, $matches);

$_SESSION['steamid'] = $matches[1];
if (!headers_sent()) {
header('Location: '.$steamauth['loginpage']);
exit;
} else {
?>
<script type="text/javascript">
window.location.href="<?=$steamauth['loginpage']?>";
</script>
<noscript>
<meta http-equiv="refresh" content="0;url=<?=$steamauth['loginpage']?>" />
</noscript>
<?php
exit;
}
} else {
echo "User is not logged in.\n";
}
}
} catch(ErrorException $e) {
echo $e->getMessage();
}
}

if (isset($_GET['logout'])){
require 'SteamConfig.php';
session_unset();
session_destroy();
header('Location: '.$steamauth['logoutpage']);
exit;
}

if (isset($_GET['update'])){
unset($_SESSION['steam_uptodate']);
require 'userInfo.php';
header('Location: '.$_SERVER['PHP_SELF']);
exit;
}


?>