I do this on my order approved/complete page by calling this php/curl function:
<?php$aff_form_data="list=19&email=" . $_SESSION['x_Email'] . "&fname=" . $_SESSION['x_First_Name'] ."&lname=" . $_SESSION['x_Last_Name'] . "&seq=1&del=1";$ch=curl_init(); curl_setopt($ch, CURLOPT_URL, "http://www.mywebsiteURL.com/m/signup.php"); curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0); curl_setopt($ch, CURLOPT_NOPROGRESS, 1); curl_setopt($ch, CURLOPT_VERBOSE, 1); curl_setopt($ch, CURLOPT_FOLLOWLOCATION,0); curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_POSTFIELDS, $aff_form_data); curl_setopt($ch, CURLOPT_TIMEOUT, 120); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);curl_setopt($ch, CURLOPT_FRESH_CONNECT, 1); $buffer = curl_exec($ch); curl_close($ch); ?>