Facebook authenticating issue , 500 server erorr - facebook

Question

From yesterday my web site getting 500 server error from facebook server side while trying to log in to the site,Im sure I have done nothing updating my code,I searched everything but havent found any solutions.
please check my code and help me.
<?php
session_start();
require 'config/fbconfig.php';
require 'facebook/facebook.php';
include"core.php";
connectdb();
$facebook = new Facebook(array(
'appId' => APP_ID,
'secret' => APP_SECRET,
));
$user = $facebook->getUser();
if ($user) {
try {
// Proceed knowing you have a logged in user who's authenticated.
$user_profile = $facebook->api('/me');
} catch (FacebookApiException $e) {
error_log($e);
$user = null;
}
if (!empty($user_profile )) {
# User info ok? Let's print it (Here we will be adding the login and registering routines)
$username = $user_profile['name'];
$uid2 = $user_profile['id'];
$email = $user_profile['email'];
$validated = mysql_fetch_array(mysql_query("SELECT COUNT(*) FROM users WHERE email='".$email."'"));
if($validated[0]== 1){
$get_data = mysql_fetch_array(mysql_query("SELECT * FROM users WHERE email='".$email."'"));
$visits = $get_data['visits'];
$visits2 = $get_data['visits']+1;
$sid= keygen(30);
mysql_query("UPDATE users SET fbid='".$uid2."', visits= '".$visits2."', sid='".$sid."' WHERE email='".$email."'");
$_SESSION['sid'] = $sid;
$expire=time()+60*60*24*30;
setcookie("sid", $_SESSION['sid'], $expire);
if($get_data['cat_sec']==0){
header('Location: cat_select.php');
exit();
}else{
if(isset($_SESSION['curl'])){
header('Location:'.$_SESSION['curl']);
}else{
header('Location: index.php');
}
exit();
}
}else{
$sid= keygen(30);
$register = mysql_query("INSERT INTO users SET fname='".$username."', email='".$email."', fbid='".$uid2."', active='1' , sid='".$sid."'");
include_once"reg_fb_mail.php";
header('Location: cat_select.php');
exit();
}
$permissions = $facebook->api("/me/permissions");
if (array_key_exists('publish_stream', $permissions['data'][0])) {
$attachment = array(
'message' => 'my web site message',
'name' => 'www.mywebsite.com!',
'caption' => "caption.",
'link' => 'http://www.website.com',
'description' => 'website description gose here ',
'picture' => 'http://website.com/images/fb.png',
'actions' => array(
array(
'name' => 'www.website.com',
'link' => 'http://www.website.com'
)
)
);
$result = $facebook->api('/me/feed/', 'post', $attachment);
}
} else {
# For testing purposes, if there was an error, let's kill the script
die("There was an error.");
}
} else {
# There's no active session, let's generate one
$login_url = $facebook->getLoginUrl(array( 'scope' => 'email,publish_stream'));
header("Location: " . $login_url);
}
?>
I have attached all the code.Please help me to sort this issue .
Thank you.

Answer 1

Error figure outs ! The issue was not at this code.In facebook settings page I found there is a single space before the APP ID . its now fixed..
Facebook dosent trim or remove white spaces from get parameters in Authentication.
If there is a invalid character its getting a 500 server error in facebook.
I think this is a critical security issue.
Hal Rotholz - Thanks for your clue..