No such host is known (no replies)

I am trying to use the PHP copy function, like this:
copy($url,$imageSave);
and I get the following error message.
"hp_network_getaddresses: getaddrinfo failed: No such host is known"

The php.ini file has: allow_url_fopen = On

Is there some way to check if a firewall is blocking the server? I am running Windows XP.