The response XML from Authorize.Net does not parse correctly as PHP5 inserts
header information before the xml data.

Quick fix solution in function.process_subscription.inc.php around line 173:


// Get rid of the rubbish at the start of the result string
// and just get the XML from the response, bypassing the header
if (!($xmlstring = strstr($result, '<?xml'))) {
        $xmlstring = null;
}

$xml = simplexml_load_string($xmlstring);

//  $xml = new SimpleXMLElement($result,LIBXML_NOWARNING);