Sample Local Proxy Server With Cors

<?php
ini_set('display_errors', 1); 
ini_set('display_startup_errors', 1); 
error_reporting(E_ALL); 



// Note, you are advised to whitelist your IP address if you are going to use such sample proxy script.
// Then, you can run this script against any target url, like: 
//        http://your_server.com/sample-proxy.php?url=https://api64.ipify.org/
class SampleProxy {

   private $whitelisted_ips = [
       'localhost',
       '127.0.0.1',
       '::1',
       // if you are accessing this script from remote device, add your ip here
   ];


   // helper function
   private function enable_cors() {
       // copied from https://stackoverflow.com/a/9866124/2377343
       if (isset($_SERVER['HTTP_ORIGIN'])) { // Allow from any origin
           // Decide if the origin in $_SERVER['HTTP_ORIGIN'] is one
           // you want to allow, and if so:
           header("Access-Control-Allow-Origin: *");
           header('Access-Control-Allow-Credentials: true');
           header('Access-Control-Max-Age: 86400');    // cache for 1 day
       }
       
       // Access-Control headers are received during OPTIONS requests
       if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
           if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
               // may also be using PUT, PATCH, HEAD etc
               header("Access-Control-Allow-Methods: GET, POST, PUT, PATCH, OPTIONS");
           if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
               header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
           exit(0);
       }
   }

   public function fetch_url ($url, $post_options = []) {
       // todo: POST method is not implemented in this example
       $ch = curl_init($url);
       curl_setopt($ch, CURLOPT_FOLLOWLOCATION	,0);
       curl_setopt($ch, CURLOPT_HEADER			,0);  // DO NOT RETURN HTTP HEADERS
       curl_setopt($ch, CURLOPT_RETURNTRANSFER	,1);  // RETURN THE CONTENTS OF THE CALL
       curl_setopt($ch, CURLOPT_HEADER, false);
       curl_setopt($ch, CURLOPT_TIMEOUT, 9);
       curl_setopt($ch, CURLOPT_SSL_VERIFYHOST,false);
       curl_setopt($ch, CURLOPT_SSL_VERIFYPEER,false);
       curl_setopt($ch, CURLOPT_MAXREDIRS, 3);
       curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 9);
       curl_setopt($ch, CURLOPT_ENCODING,  '');
       $response = curl_exec($ch);
       curl_close($ch);
       return $response;
   }

   
   public function __construct() {
       if (!in_array($_SERVER['REMOTE_ADDR'], $this->whitelisted_ips)) {
           die("Your IP is forbidden... " . strval($_SERVER['REMOTE_ADDR']));
       }
       $this->enable_cors();
       echo $this->fetch_url(filter_var($_GET['url'], FILTER_SANITIZE_URL));
       exit(0);
   }
}

new SampleProxy();