Silex - Let NGINX handle static files after authentication with PHP

1-example.com.conf

server {
    listen          80;
    listen          [::]:80;
    server_name     example.com;

    root            /var/www/project/web;
    index           index.php;

    # catches internal redirects from php with 'X-Accel-Redirect' header
    location /private_admin_files {
        # and forwards them to this path:
        alias /var/www/project/src/statics/admin
        internal;
    }

    location / {
        # Check if requested file is present and use if for procesing.
        # Otherwise, fall back to index.php
        try_files $uri /index.php$is_args$args;
    }

    location ~ \.php$ {
        # regex to split $uri to $fastcgi_script_name and $fastcgi_path
        fastcgi_split_path_info ^(.+\.php)(/.*)$;

        # Check if requested file is present and use if for procesing.
        # Otherwise, fall back to index.php
        try_files $uri /index.php$is_args$args;

        # Bypass the fact that try_files resets $fastcgi_path_info
        # see: http://trac.nginx.org/nginx/ticket/321
        set $path_info $fastcgi_path_info;

        # serve index.php in case '/' is requested
        fastcgi_index index.php;

        # use socket
        fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;

        include fastcgi_params;
    }
}

2-StaticFileController.php

<?php

use Silex\Application;
use Symfony\Component\HttpFoundation\Response;

class StaticFileController
{
    /**
     * @param Application $app
     * @param string $file                     filename of file to serve
     * @param string $folder                   folder of the file to serve
     * @param string $virtiualXAccelRedirPath  virtual X-Accel-Redirect path as used in vhost
     *
     * This will return an empty response with the right X-Accel-Redirect header.
     * NGINX will use this header and will match it's value against all location as defined
     * in it's vhost.
     *
     * For example:
     *
     *   $file                     = 'admin.js'
     *   $folder                   = __DIR__ . '/../statics/admin/'
     *   $virtiualXAccelRedirPath  = '/private_admin_files'
     *
     * NGINX vhost config has a location block like:
     *
     *   location /private_admin_files {
     *       alias /path/to/project/src/statics/admin/
     *       internal;
     *   }
     *
     * This method will send a response with
     *
     *   X-Accel-Redirect: /private_admin_files/admin.js
     *
     * And NGINX will rewrite it to
     *
     *   /path/to/project/src/statics/admin/admin.js internally
     *
     * and will serve the requested file without much PHP overhead!
     *
     * @return Response
     */
    public function getFile(Application $app, $file = '', $folder = '', $virtiualXAccelRedirPath = '')
    {
        if (empty($file) || empty($folder) || empty($virtiualXAccelRedirPath)) {
            $app->abort(400);
        }

        // add slash if string does not end in slash
        if (substr($folder, -1) !== '/') {
            $folder .= '/';
        }
        if (substr($virtiualXAccelRedirPath, -1) !== '/') {
            $virtiualXAccelRedirPath .= '/';
        }

        if (!is_readable($folder . $file)) {
            $app->abort(404, 'file not readible ' . $folder . $file);
        }

        switch (strtolower(pathinfo($file, PATHINFO_EXTENSION))) {
            case 'css' : {
                $contentType = 'text/css';
                break;
            }
            case 'js' : {
                $contentType = 'application/javascript';
                break;
            }
            case 'xml' : {
                $contentType = 'text/xml';
                break;
            }
            case 'svg' : {
                $contentType = 'image/svg+xml';
                break;
            }
            default : {
                $contentType = 'text/plain';
            }
        }

        return new Response('', 200, [
            'X-Accel-Redirect' => $virtiualXAccelRedirPath . $file,
            'Content-Type' => $contentType
        ]);
    }
}

3-Routing.php

use Silex\Application;
use Silex\Api\ControllerProviderInterface;
use Symfony\Component\HttpFoundation\Request;

class Routing implements ControllerProviderInterface
{
    public function connect(Application $app)
    {
        $controllers = $app['controllers_factory'];

        $controllers->get('/', 'IndexController::getPage');
        // ... more controllers

        $app->mount('/admin', new AdminRouting());

        return $controllers;
    }
}

4-AdminRouting.php

use Silex\Application;
use Silex\Api\ControllerProviderInterface;
use Symfony\Component\HttpFoundation\Request;

class AdminRouting implements ControllerProviderInterface
{
    public function connect(Application $app)
    {
        $controllers = $app['controllers_factory'];
        $controllers->before(function (Request $request, Application $app) {
            // check auth or abort! 
        });

        $controllers->get('/', 'AdminController::getIndex');

        $controllers->get('/static/{file}', 'StaticFileController::getFile')
            ->assert('file', '.+')
            ->value('folder', __DIR__ . '/../statics/admin')
            ->value('virtiualXAccelRedirPath', '/private_admin_files');

        return $controllers;
    }
}