index.php

<?php
require_once __DIR__.'/../symfony/app/bootstrap.php.cache';
require_once __DIR__.'/../symfony/app/AppKernel.php';

use Symfony\Component\HttpFoundation\Request;

$kernel = new AppKernel('dev', true);
$kernel->loadClassCache();

$response = $kernel->handle(Request::createFromGlobals());

// check to see if a route match in Symfony 2
if($response->getStatusCode() !== 404) {
    // if do, send continue Symfony 2 app
    $response->send();
} else {
    // if there is no match, bootstrap and forward to Wordpress

    // tells WordPress to load the WordPress theme and output it.
    define('WP_USE_THEMES', true); 

    // loads the WordPress Environment and Template
    require('./wp-blog-header.php');
}