title: Unable to login through facebook php sdk
body: <p>While login wiht fb php sdk, I am getting such kind of error
  This page isn’t working</p>
  
  <p>www.facebook.com is currently unable to handle this request.
  HTTP ERROR 500</p>
  
  <p>I had configure my app and my secret key properly according to facebook app and key.</p>
  
  <p>I am not getting why such kind of error is thrown. Please Help me</p>
  
  <pre><code>// init app with app id and secret
     FacebookSession::setDefaultApplication( 
       myappkey,mysecretkey );
    // login helper with redirect_uri
     $helper = new 
    FacebookRedirectLoginHelper('http://demos.krizna.com/1353/fbconfig.php' );
    try {
    $session = $helper-&gt;getSessionFromRedirect();
   } catch( FacebookRequestException $ex ) {
    // When Facebook returns an error
   } catch( Exception $ex ) {
    // When validation fails or other local issues
   }
     // see if we have a session
   if ( isset( $session ) ) {
    // graph api request for user data
   $request = new FacebookRequest( $session, 'GET', '/me' );
   $response = $request-&gt;execute();
   // get response
      $graphObject = $response-&gt;getGraphObject();
      $fbid = $graphObject-&gt;getProperty('id');              // To Get Facebook ID
      $fbfullname = $graphObject-&gt;getProperty('name'); // To Get Facebook full name
      $femail = $graphObject-&gt;getProperty('email');    // To Get Facebook email ID
  /* ---- Session Variables -----*/
      $_SESSION['FBID'] = $fbid;           
      $_SESSION['FULLNAME'] = $fbfullname;
      $_SESSION['EMAIL'] =  $femail;
  /* ---- header location after session ----*/
      header("Location: index.php");
  } else {
    $loginUrl = $helper-&gt;getLoginUrl();
   header("Location: ".$loginUrl);
  }
  </code></pre>