Warning: Undefined variable $fp in C:\xampp\htdocs\account\login.php on line 50

Fatal error: Uncaught TypeError: fwrite(): Argument #1 ($stream) must be of type resource, null given in C:\xampp\htdocs\account\login.php:50 Stack trace: #0 C:\xampp\htdocs\account\login.php(50): fwrite(NULL, 'IP: 18.217.207....') #1 C:\xampp\htdocs\pages\rankingsweek.php(72): include('C:\\xampp\\htdocs...') #2 {main} thrown in C:\xampp\htdocs\account\login.php on line 50