I'd recommend using PHP's cURL Library (A lot of great documentation and user-examples available @ php.net). You will need to "spoof" your user agent to look like Internet Explorer or Firefox (or any supported browser)
Some sites may use more advanced methods of detection to tell if it's an actual request, including the referral header.
// spoofing FireFox 2.0
$useragent="Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:18.104.22.168) Gecko/20061204 Firefox/22.214.171.124";
// Get curl handle
$ch = curl_init();
// set user agent
curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
Let me know if it worked out for you!