Docusign REST call from CodeIgniter

Docusign REST call from CodeIgniter

I'm trying to call the DocuSign REST login information within a
CodeIgniter application. The Docusign sample code shows:
// Input your info here:
$integratorKey = '...';
$email = '...@....com';
$password = '...';
$name = 'John Doe';
// construct the authentication header:
$header = "<DocuSignCredentials><Username>" . $email .
"</Username><Password>" . $password . "</Password><IntegratorKey>" .
$integratorKey . "</IntegratorKey></DocuSignCredentials>";
/////////////////////////////////////////////////////////////////////////////////////////////////
// STEP 1 - Login (to retrieve baseUrl and accountId)
/////////////////////////////////////////////////////////////////////////////////////////////////
$url = "https://demo.docusign.net/restapi/v2/login_information";
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_HEADER, false);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_HTTPHEADER, array("X-DocuSign-Authentication:
$header"));
$json_response = curl_exec($curl);
$status = curl_getinfo($curl, CURLINFO_HTTP_CODE);
if ( $status != 200 ) {
echo "error calling webservice, status is:" . $status;
exit(-1);
}
I keep getting a status response of 0. When I echo out the curl all the
xml tags have been converted to lowercase (which won't work with
Docusign). Has anyone done this call within CodeIgniter? How did you
accomplish it? I know my credentials are good because I can do a command
line curl and get a response.