redirector.php

<?php
$url = $_GET['r'];
$encoded_url = preg_replace_callback(
	'#://([^/]+)/([^?]+)#', 
	function ($match) {
		return 
      '://' . 
      $match[1] . 
      '/' . 
      join(
        '/', 
        array_map('rawurlencode', explode('/', $match[2]))
      );
	}, 
  $url
);
	
if (filter_var($encoded_url, FILTER_VALIDATE_URL)) {
   header("Location: {$encoded_url}");
} else {
   header("Status: 400 Bad Request");
}