simple code to require OpenID authentication on a page

simplePhpOpenid.php

<?php // simple code to require OpenID authentication on a page

/*
Requirements:
* PHP 5
* OpenID Enabled PHP library (http://openidenabled.com/php-openid/)

Usage:
1) Put this code in a file on your server
2) Edit the "$realm" variable to be your domain
3) Load the page in a browser
4) Log into Yahoo! after being redirected
*/

//suppress warnings caused by php openid lib as we need to redirect
error_reporting(E_ERROR | E_PARSE);

//php openid lib requires session
session_start();

//ammend include path so we can include files consistently
$includePath = get_include_path().PATH_SEPARATOR.'php-openid-2.1.3';
set_include_path($includePath);

//include openid files
//get openid lib from http://openidenabled.com/php-openid/
require_once "Auth/OpenID/Consumer.php";
require_once "Auth/OpenID/FileStore.php";
require_once "Auth/OpenID/AX.php";
        
//init basic openid auth url generation
$openidFileStore = new Auth_OpenID_FileStore('/tmp/');
$openidConsumer =& new Auth_OpenID_Consumer($openidFileStore);

//safely fetch input
$filters = array(
    'openid_identity' => FILTER_SANITIZESTRING,
    'openid_mode' => FILTER_SANITIZESTRING,
    'username' => FILTER_SANITIZESTRING,
);
$input = filter_var_array( $_REQUEST, $filters );

//settings
$realm = 'http://example.com';
$openidProvider = 'http://yahoo.com/';

//if the user's not logged in, and there is an openid assertion param in the url, verify response
if ( !$input['username'] && 'id_res' == $input['openid_mode'] ) {
    
    $verification = $openidConsumer->complete( $realm.$_SERVER['REQUEST_URI'] );
    
    if ( 'success' == $verification->status ) {
        setcookie('username', $input['openid_identity'] );
        $input['username'] = $input['openid_identity'];
    } else {
        var_dump( $verification );
    }
    
//if the user's not logged in, redirect to log in
} elseif ( !$input['username'] ) {
    
    $openidAuthRequest = $openidConsumer->begin( $openidProvider );

    $openidLoginRedirectUrl = $openidAuthRequest->redirectURL(
        $realm,
        $realm.$_SERVER['REQUEST_URI']
    );
    
    header( 'Location: '.$openidLoginRedirectUrl );  
} 
?>

Welcome, <?= $input['username'] ?>