/* in site config */
$Config['siteSalt'] = 'ksjh2k234jk45kj4uo8vxoise8';

function hashSteamId($steamId){
  global $Config;
  return sha1($steamId . $Config['siteSalt']);
}


/* login.php */
if(isset($_GET['openid_claimed_id'])){
  $steamId = SteamSignIn::validate();
  //if successful login
  if($steamId){
    $hash = hashSteamId($steamId);
    $cookieData = $steamId.'|'.$hash;
    setcookie('user', $cookieData, time()+60*60*24*365); //sets the cookie for a year
    echo 'Successfully logged in';
    exit;
  }
  echo 'Failed to validate login';
  exit;
}

echo '<a href="'.SteamSignIn::genUrl().'">login</a>';


/* on each page load */
//tries to load the logged in user. format should be 'steamId|hash'
$userCookieData = filter_input(INPUT_COOKIE, 'user', FILTER_DEFAULT, FILTER_REQUIRE_SCALAR);
if($userCookieData){
  //loads the steam id (all data before the "|")
  $userSteamId = strtok($userCookieData, '|');
  //loads the hash (the rest of the str in $userCookieData)
  $userSteamHash = strtok('');

  //checks the hash supplied against what it should be
  if($userSteamHash === hashSteamId($userSteamId)){
    //is valid login. do stuff
  }
}


/* logout.php */
//deletes the cookie
setcookie('userId', 0, time()-60*60*24*30);