Facebook PHP Logout Example Code to only logout user from app and not from Facebook. Essentially revoke the permission from your app.

logout.php

<?php
require '../src/facebook.php';

// Create our Application instance (replace this with your appId and secret).
$facebook = new Facebook(array(
  'appId'  => '<appid>',
  'secret' => '<appsecret>',
));

// Get User ID
$user = $facebook->getUser();

if($user)
{
	$permissions = $user.'/permissions';
	$facebook->api($permissions, "DELETE");
	session_destroy();
	header("Location: example.php");
	die();
}

?>