fb app system: inc/fb.php

<?php
require_once 'lib/facebook.php';
require_once 'functions.php';
$facebook = new Facebook(array('appId'=>APP_ID,'secret'=>APP_SECRET,'fileUpload'=>true,'cookie'=>true));
$user     = $facebook->getUser();
if($user)
{
try
{
$user_profile = $facebook->api('/me');
}
catch(FacebookApiException $e)
{
error_log($e);
$user = null;
}
}
if ($user)
{
$logoutUrl = $facebook->getLogoutUrl();
}
else
{
//======================================== PEYMENT ========================================//