PHP caching proxy

cache-proxy.php

<?php

if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
  header('Access-Control-Allow-Origin: *');
  header('Access-Control-Allow-Methods: GET, OPTIONS');
  header('Access-Control-Allow-Headers: accept, x-requested-with, content-type');
  exit();
}

$url = $_GET['url'];
$file = __DIR__ . '/../app/data/' . hash('sha256', $url);

function output_headers($file) {
  $info = json_decode(file_get_contents($file . '.json'), true);

  http_response_code($info['http_code']);
  header('Access-Control-Allow-Origin: *');
  header('Content-Type: ' . $info['content_type']);
  header('Content-Length: ' . filesize($file));
  //header('Content-Length: ' . $info['download_content_length']);
}

if (file_exists($file)) {
  output_headers($file);
  readfile($file);
  exit();
}

$headers = getallheaders();

$output = fopen($file, 'w');

$curl = curl_init($url);
curl_setopt($curl, CURLOPT_VERBOSE, true);
curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($curl, CURLOPT_ENCODING, '');
curl_setopt($curl, CURLOPT_HTTPHEADER, array_map(function($value, $key) {
  if (!in_array($key, array('Origin', 'Referer', 'Connection', 'Host'))) {
    return $key . ':' . $value;
  }
}, $headers, array_keys($headers)));
curl_setopt($curl, CURLOPT_FILE, $output);
curl_exec($curl);
file_put_contents($file . '.json', json_encode(curl_getinfo($curl), JSON_PRETTY_PRINT));
curl_close($curl);
fclose($output);

output_headers($file);
readfile($file);
exit();