Warning: Undefined array key "domain" in D:\xampp\htdocs\whois\getwhois.php on line 13

Fatal error: Uncaught TypeError: Whois::getWhoisServerDetails(): Argument #1 ($domain) must be of type string, null given, called in D:\xampp\htdocs\whois\getwhois.php on line 26 and defined in D:\xampp\htdocs\whois\whois_class.php:165 Stack trace: #0 D:\xampp\htdocs\whois\getwhois.php(26): Whois->getWhoisServerDetails(NULL) #1 {main} thrown in D:\xampp\htdocs\whois\whois_class.php on line 165