ปัญหาเฟส บุ๊ค ใช้คำสั่ง $facebook- getuser returns 0 ไม่ได้ข้อมูลอะไรเลย

<?php
session_start();
include("facebook.php"); 

$facebook = new Facebook(
	array(
		'appId'  => '126329007486275', 
		'secret' => 'fda320277b2d1b71d62bfce847786e92',
                'fileUpload' => true,
		'cookie' => true,  
));
echo $fb_user = $facebook->getUser();

if($fb_user){         
	try{
		$fb_userData = $facebook->api('/me','GET');
	}
	catch(FacebookApiException $e) { 
		error_log($e);
		$user=null;
		error_log($e->getType());
		error_log($e->getMessage());
	}
}

if(isset($_GET['logout'])){ 
	$facebook->destroySession(null); 
	header("Location:".$_SERVER['PHP_SELF']);
}

	$logoutUrl = $facebook->getLogoutUrl(
		array(
			"next"=>"http://www.smileprogramming.com/contest/user/logout.php"
		)
	);
?>

<? if ($fb_user) {
						$logoutUrl = $facebook->getLogoutUrl(array("next" => "http://smileimgcontest.co.cc/user/logout.php"));
						try {
							$userdata = $facebook->api('/me');
						} catch (FacebookApiException $e) {
							error_log($e);
							$user = null;
						}
						$_SESSION['facebook'] = $_SESSION;
						$_SESSION['userdata'] = $userdata;
						$_SESSION['logout'] =  $logoutUrl;
						header("Location:action.php?file=chk_login_up&imgContest_id=$imgCont&img_url=$imgUrl");
					}
					else {
						$loginUrl = $facebook->getLoginUrl(
								array(
									"redirect_uri"=>"http://www.smileprogramming.com/contest/user/after_fb.php?send_fb=".$send_fb."",
									"display"=>"popup",
									"scope"=>"offline_access,publish_stream,email,user_about_me,user_birthday,user_photos" 
								)
							);
						echo '<div style="padding:50px 0 0 125px;"><a href="'.$loginUrl.'"><img src="stylesheet/pic/fblogin_btn.png" /></a></div>';
					}
					?>

<?
include "../include/connect_db.php";
include "lib/fbconfig.php";
/*$f_name =  $fb_userData[first_name];
$l_name = $fb_userData[last_name];  
$e_mail =  $fb_userData[email];
$gender =  $fb_userData[gender];
$b_day = $fb_userData[birthday]; 
$ar_b_day = explode('/',$b_day ); 
$r_b_day =  $ar_b_day[2]."-".$ar_b_day[0]."-".$ar_b_day[1];
$picture = $fb_userData[id]; 
$status = 0;
?>