php file_get_contents

any idea why my server adds at least 5 seconds to my php scripts that use domains ...

$page_data = file_get_contents("http://domain.com/fileget2.php");

using this method, timing with microtime()

it takes (5.013 seconds) to load a small 4 lines of text

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but if I use the IP address there is no 5 second interval

$page_data = file_get_contents("http://IP.IP.IP.IP/~y45hund/fileget2.php");

it takes (0.013 seconds) to load a small 4 lines of text

I guess this might be nameservers issue, however, my host provider is all but helpful in resolving this issue.