public function __construct($domain, $server)
 {
     $this->domain = $domain;
     $this->server = $server;
     parent::__construct("nslookup -timeout=3 {$domain} {$server}");
 }
 public function __construct($url)
 {
     $this->url = $url;
     parent::__construct("curl --connect-timeout 3 {$this->url}");
 }
 public function __construct($ip)
 {
     $this->ip = $ip;
     parent::__construct("/bin/ping -c 1 -W 3 {$this->ip}");
 }