yeah like Erkilite said if you have curl you can try:
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://www.site.com/page.ext");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, "x=1&y=2&z=3");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_TIMEOUT, 10);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0); //dont verify cert
curl_setopt($ch, CURLOPT_REFERER, "http://yoursite.com");
curl_setopt($ch, CURLOPT_USERAGENT, "mozilla 4.0");
$data = curl_exec($ch);
curl_close($ch);
for more curl options see http://us2.php.net/manual/en/function.curl-setopt.php