how to include facebook sdk initial?

Hi I'm beginner in Codeigniter. I have 4 view page that have facebook login (1. login page 2.register page 3.login special member page 4.register special member page)
And all 4 views file I have to initial facebook php sdk like this

Code:

<?php require_once(APPPATH.'libraries/facebook/src/facebook.php');
$facebook = new Facebook(array(
 'appId'  => 'xxxxxxxxxxxxxx',
 'secret' => 'xxxxxxxxxxxxxxxxxxxxxxxxxxxx',
));


$user = $facebook->getUser();

It's very annoying that one day I have to change appID and appsecret, I have to change it in 4 view files.
so I create new view file name "fb_init.php" that contain code

Code:

<?php require_once(APPPATH.'libraries/facebook/src/facebook.php');
   $facebook = new Facebook(array(
     'appId'  => 'xxxxxxxxxxxxxxxx',
     'secret' => 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
   ));


   $user = $facebook->getUser();

and then in 4 view files I include fb_init.php by write

Code:

$this->load->view('fb_init.php');

However, The problem is the remaining code of facebook php sdk cannot refer to 

Code:

$user

 variable. the remaining code of facebook sdk is here.

Code:

   if ($user) {
     try {
       // Proceed knowing you have a logged in user who's authenticated.
       $user_profile = $facebook->api('/me?fields=id,email,name,first_name,last_name,picture'); //ต้องมีหลัง /me ไม่งั้นประวัติมาไม่ครบ
     } catch (FacebookApiException $e) {
       error_log($e);
       $user = null;
     }
   }

$loginUrl = $facebook->getLoginUrl(array(  
   "redirect_uri"=>"http://www.club55.net/login",  
   "scope"=>"email"
 ));

How could I do?