[PHP] Question about function dns_check_record

[Bao Vu]

Hello,

I have a problem regard to function
   - dns_check_record
   - dns_get_mx
Can you tell me why the PHP said the "Call to undefined function"?
 
and also

class Dog
{
   function __construct()
   {
   }
}

the construct or descontruction are not working?

Thanks,
Bao