Notes

<?php
require 'includes/lightopenid/openid.php';
$_STEAMAPI = "YOURSTEAMAPIKEY";
try
{
$openid = new LightOpenID('http://URL.TO.REDIRECT.TO.AFTER.LOGIN/');
if(!$openid->mode)
{
if(isset($_GET['login']))
{
$openid->identity = 'http://steamcommunity.com/openid/?l=english'; // This is forcing english because it has a weird habit of selecting a random language otherwise
header('Location: ' . $openid->authUrl());
}
?>
<form action="?login" method="post">
<input type="image" src="http://cdn.steamcommunity.com/public/images/signinthroughsteam/sits_small.png">
</form>
<?php
}
elseif($openid->mode == 'cancel')
{
echo 'User has canceled authentication!';
}
else
{
if($openid->validate())
{
$id = $openid->identity;
// identity is something like: http://steamcommunity.com/openid/id/76561197960435530
// we only care about the unique account ID at the end of the URL.
$ptn = "/^http://steamcommunity.com/openid/id/(7[0-9]{15,25}+)$/";
preg_match($ptn, $id, $matches);
echo "User is logged in (steamID: $matches[1])n";

$url = "http://api.steampowered.com/ISteamUser/GetPlayerSummaries/v0002/?key=$_STEAMAPI&steamids=$matches[1]";
$json_object= file_get_contents($url);
$json_decoded = json_decode($json_object);

foreach ($json_decoded->response->players as $player)
{
echo "
<br/>Player ID: $player->steamid
<br/>Player Name: $player->personaname
<br/>Profile URL: $player->profileurl
<br/>SmallAvatar: <img src='$player->avatar'/>
<br/>MediumAvatar: <img src='$player->avatarmedium'/>
<br/>LargeAvatar: <img src='$player->avatarfull'/>
";
}

}
else
{
echo "User is not logged in.n";
}
}
}
catch(ErrorException $e)
{
echo $e->getMessage();
}
?>