Sign in with Steam PHP

gistfile1.php

class AuthController {
	const STEAM_LOGIN = 'https://steamcommunity.com/openid/login';
	const STEAM_API_FORMAT = "json";
 
	public static function genUrl($returnTo = false) {
		$returnTo = (empty($_SERVER['HTTPS']) ? "http" : "https") . "://" . $_SERVER['HTTP_HOST'] . $_SERVER['SCRIPT_NAME'];
		
		$params = array(
			'openid.ns'		=> 'http://specs.openid.net/auth/2.0',
			'openid.mode'		=> 'checkid_setup',
			'openid.return_to'	=> $returnTo,
			'openid.realm'		=> (!empty($_SERVER['HTTPS']) ? 'https' : 'http') . '://' . $_SERVER['HTTP_HOST'],
			'openid.identity'	=> 'http://specs.openid.net/auth/2.0/identifier_select',
			'openid.claimed_id'	=> 'http://specs.openid.net/auth/2.0/identifier_select',
		);
		
		return self::STEAM_LOGIN . '?' . http_build_query($params, '', "&");
	}
 
	public static function authenticate() {
		if (isset($_SESSION['user_id'])) return true;
		
		$params = array(
			'openid.assoc_handle'	=> $_GET['openid_assoc_handle'],
			'openid.signed'			=> $_GET['openid_signed'],
			'openid.sig'			=> $_GET['openid_sig'],
			'openid.ns'				=> 'http://specs.openid.net/auth/2.0',
		);
		
		$signed = explode(',', $_GET['openid_signed']);
		foreach($signed as $item) {
			$val = $_GET['openid_' . str_replace('.', '_', $item)];
			$params['openid.' . $item] = get_magic_quotes_gpc() ? stripslashes($val) : $val; 
		}
 
		$params['openid.mode'] = 'check_authentication'; // Finally, add the all important mode. 
		
		$data =  http_build_query($params);
		$context = stream_context_create(array(
			'http' => array(
				'method'  => 'POST',
				'header'  => 
					"Accept-language: en\r\n".
					"Content-type: application/x-www-form-urlencoded\r\n" .
					"Content-Length: " . strlen($data) . "\r\n",
				'content' => $data,
			),
		));
 
		$result = file_get_contents(self::STEAM_LOGIN, false, $context);
		
		
		preg_match("#^http://steamcommunity.com/openid/id/([0-9]{17,25})#", $_GET['openid_claimed_id'], $matches); // Validate wheather it's true and if we have a good ID
		$steamID64 = is_numeric($matches[1]) ? $matches[1] : 0;
 
		if (preg_match("#is_valid\s*:\s*true#i", $result) == 1) $profile = self::getProfile($steamID64);
		else { 
			error("could not authenticate with Steam...", false);
			return false;
		}
 
		if ($profile['user_id'] == "") $profile['user_id'] = $profile['steam_id'];
		if ($profile['user_id'] != "") {
			// username not empty - do something here with the username
		}
 
		$_SESSION['user_id'] = $user['user_id'];
		return true;
	}
 
	public static function getProfile($steamID64) {
		$context = stream_context_create(array('http' => array('method'  => 'GET')));
		$result = file_get_contents("http://steamcommunity.com/profiles/" . $steamID64 . "?xml=1", false, $context);
		xml_parse_into_struct(xml_parser_create(), $result, $result, $indexes);
 
		return array('user_id' => $result[$indexes["CUSTOMURL"][0]]['value'], 'steam_id' => $result[$indexes["STEAMID"][0]]['value'], 'steamID64' => $steamID64);
	}
}