Ошибка в скрипте

Код (Text):

1. <?php
2.  
3. $uri = $_GET['f'];
4.  
5. $url = "https://icer.ink/media1.clubpenguin.com/play/$uri";
6.  
7. $data = file_get_contents($url);
8. $headers = get_headers($url, true);
9.  
10. header($headers["Content-Type"]);
11.  
12. $directory = dirname($uri);
13.  
14. if(!is_dir($directory)) {
15.     mkdir($directory, 0777, true);
16. }
17.  
18. file_put_contents($uri, $data);
19.  
20. echo $data;
21.  
22. ?>

Код (Text):

1. Notice: Undefined index: f in C:\xampp\htdocs\media1\play\media-server.php on line 3
2.  
3. Warning: mkdir(): Invalid path in C:\xampp\htdocs\media1\play\media-server.php on line 15
4.  
5. Warning: file_put_contents(): Filename cannot be empty in C:\xampp\htdocs\media1\play\media-server.php on line 18