If you're having problems with fopen("url...") but you can run 'host url' in a shell window and get the correct lookup, here's why...
This has had me banging my head against it all day - finally I found the answer buried in the bug reports, but figured it should really be more prominent!
The problem happens when you're on an ADSL line with DHCP (like our office)... When the ADSL modem renews the DHCP lease, you can also switch DNS servers, which confuses apache (and hence PHP) - meaning that you can't look up hosts from within PHP, even though you *can* from the commandline.... The short-term solution is to restart apache.
You'll get "php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution in ..." messages as symptoms. Restart apache, and they're gone :-)
Warning: main(http://camf.ivyro.net/preload/preload_out.php): failed to open stream: HTTP request failed! HTTP/1.1 404 Not Found in /home1/camf/public_html/index3.htm on line 136
Warning: main(): Failed opening 'http://camf.ivyro.net/preload/preload_out.php' for inclusion (include_path='.:/usr/local/php/lib/php') in /home1/camf/public_html/index3.htm on line 136