It seem if you pass invalid host name to fsockopen, and you are online, script crashes. If offline all is ok.
Example:
$sock = fsockopen($ns, 53, $error, $errstr, 60);

if(!$sock) {
   printf("Nije uspela konekcija!<br>\n");
   return -1;
} 
else {
}

if ns is invalid like yuo have 2 dots in name script do a printf and exit's form script (this was a function).
It seems if lookup fails, there are problems.