Why does my Facebook app isn't loading pages? - php

Question

I'm making an app on Facebook using WordPress and everything is fine, I'm on the front page of the app, but when I try to access a link to another page of my app in Mozilla Firefox shows a blank page and in Google Chrome stays on the front page.
Has anyone an idea of why this is happening? Has anyone encountered this behaviour?
My next code is used by me in the WordPress root index.php, not the front page index.php, to request permissions of the user before entering the app:
<?php
/**
* Front to the WordPress application. This file doesn't do anything, but loads
* wp-blog-header.php which does and tells WordPress to load the theme.
*
* #package WordPress
*/
/**
* Tells WordPress to load the WordPress theme and output it.
*
* #var bool
*/
session_start();
require 'src/facebook.php';
// LOGIN
$app_details = array('app_id' => 'secret',
'app_secret' => 'secret',
'page_link' => '//www.facebook.com/secret/'
);
$http = "http:";
if(isset($_SERVER['HTTPS']))
if (!empty($_SERVER['HTTPS'])) $http = "https:";
$facebook = new Facebook(array(
'appId' => $app_details['app_id'],
'secret' => $app_details['app_secret'],
'cookie' => true
));
$the_signed_request = $facebook->getSignedRequest();
if ($the_signed_request == null) {
header("Location: ".$http.$app_details['page_link']."app/".$app_details['app_id']);
}
if ( !isset($the_signed_request['user_id']) && !isset($the_signed_request['oauth_token']) ){
$loginUrl = $facebook->getLoginUrl(array('scope'=>'email'));
if (!isset($_SESSION['rejects'])) $_SESSION['refuzuri'] = 0;
else $_SESSION['rejects']++;
if ($_SESSION['rejects']>4) {
echo "This app works only if permissions are accepted.<br/>";
echo "To accept the permissions <a href='".$loginUrl."' target='_top'>click here</a>";
die();
}
echo( "<script>top.location.href='" . $loginUrl . "';</script>" );
}else{
try{
$access_token = $facebook->getAccessToken();
$user = $facebook->getUser();//userid
$userinfo = $facebook->api('/me?fields=id,name,email,gender,locale'); //for basic details
}catch (FacebookApiException $e) {
$user = null;
$userinfo = null;
}
$_SESSION['user']= $userinfo;
define('WP_USE_THEMES', true);
/** Loads the WordPress Environment and Template */
require( dirname( __FILE__ ) . '/wp-blog-header.php' );
}
?>