index.php

<?php require_once __DIR__.'/../vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\File\UploadedFile;

use Silex\Application;

$app = new Application();
$app['debug'] = true;

$upload_dir = "../files";

$app->get('/are you there', function (Request $request) {
  return new Response('<pre>[file server] Yes...</pre>');
});

/**
 * Returns file if exists, 404 if not.
 */
$app->get('/{filename}', function (Request $request, $filename) use ($app, $upload_dir) {
  return $app->sendFile("{$upload_dir}/{$filename}");
});

/**
 * File upload end point, writes files to file system if they don't exist.
 */
$app->post('/upload', function (Request $request) use ($app, $upload_dir) {
  $code = Response::HTTP_OK;  // 200;
  $body = [
    'error' => 'none',
    'message' => 'Upload complete',
    'files' => [],
  ];

  // First check all files for conflicts.
  foreach ($request->files as $file) {
    $filename = getFilename($file);
    if (file_exists("{$upload_dir}/{$filename}")) {
      $code = Response::HTTP_CONFLICT; // 409;
      $body['error'] = 'conflict';
      $body['message'] = 'File already exists';
      $body['files'][] = $filename;
    }
  }

  if ($code === Response::HTTP_OK) {
    // No conflicts: safe to save files.
    foreach ($request->files as $file) {
      $filename = getFilename($file);
      $file->move($upload_dir, $filename);
      $body['files'][] = $filename;
    }
  }

  error_log(print_r($request->files, 1) . "\n" . print_r($body, 1));

  return new Response('', $code);

  // TODO: Not bothering returning JSON, status code should be sufficient.
  // return $app->json($body, $code);
});

// Respond to OPTIONS requests for CORS, Apache sets the headers (via .htaccess).
$app->options('/{uuid}', function (Request $request) { return new Response(); });
$app->options('/upload', function (Request $request) { return new Response(); });

$app->run();

function getFilename(UploadedFile $file) {
    // TODO: Handle filename & extension sanitization / rejection.
    $fileName = $file->getClientOriginalName();
    return $fileName;
}