Options for the underlying resolver functions can be supplied by using the RES_OPTIONS environmental variable. (at least under Linux, see man resolv.conf)
Set timeout and retries to 1 to have a maximum execution time of 1 second for the DNS lookup:
<?php
putenv('RES_OPTIONS=retrans:1 retry:1 timeout:1 attempts:1');
gethostbyname($something);
?>
You should also use fully qualified domain names ending in a dot. This prevents the resolver from walking though all search domains and retrying the domain with the search domain appended.
