function validate_facebook_session($args, $app_secret) {
$payload = '';
ksort($args);
foreach ($args as $key => $value) {
if ($key != 'sig') {
$payload .= $key . '=' . $value;
}
}
$hash_in = $payload . $app_secret;
$sig = $args['sig'];
if (md5($hash_in) != $sig) {
return null;
}
return $args;
}