DNS querys slow when using PHP and Perl in Apache

Hi Group.

I've got a strange problem with my apache webserver.

When i call a script like

<?
gethostbyname("foo.bar") ;
?>

via /usr/local/bin/php /home/foo/html/dnstest.php it takes not a sec.

But when i call the same script via http://localhost/foo/dnstest.php it
takes about 5 sec. to get a result.
At first i think the problem was PHP. But now i tried it with perl. And the
same happens.
A nslookup foo.bar is also fsat so my nameserver is reachable.

It must be something in my Apache config. PHP and PERL is called by
module.so

I use Apache2 / PHP 4.3.4 / RH 7.2

Maybe you can help me.
Regards Rene