One of our customers had us help them with curl... not with skipjack but a similar credit card prog. Here's the code that worked for them:
dl("curl.so");
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://secure.iongate.com/iongate.asp");
curl_setopt ($ch, CURLOPT_POST, 1); // simulate a post
curl_setopt($ch, CURLOPT_POSTFIELDS, $pairs); // "a=3&b=5"
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); // return data, no print
curl_setopt($ch, CURLOPT_HEADER, 0); // dont give http headers in output
curl_setopt($ch, CURLOPT_USERAGENT,
"Mozilla/4.0 (compatible; MSIE5.01; Windows NT 5.0)"); // for fun
$result = curl_exec($ch);
curl_close ($ch);
// You POSTed
--
John Masterson
http://www.modwest.com