if($_POST['form']['user_amount'] != ''){
$aantal = $_POST['form']['user_amount'];
} else {
$aantal = '1250';
}
 
## Request an External link
$ch = curl_init();
$data = array(
'user_api_key' => 'KEY IS HERE',
'user_id' => 'IDNUMBER IS HERE',
'user_reference_key' => 'OTHER DIGIT KEY HERE',
'amount_cents' => $aantal,
'remark' => 'Aantal',
'webhook_notification_url' => 'http://mywebsite/index.php?option=com_rsform&formId=6',
'on_topup_success_url' => 'http://mywebsite/success',
'on_topup_failure_url' => 'http://mywebsite/failure'    
);
curl_setopt($ch, CURLOPT_URL, 'https://external url to post to');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/x-www-form-urlencoded'));   
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); 
$json_response = curl_exec($ch);
 
// get link 
$response_obj = json_decode($json_response);
$exterlink = $response_obj->{'exterlink'}; 
 
## Redirect the user to external page

// Order is significant here. Name first, Email as second parameter:
 
$data = array(
'name' => $_POST['form']['name'], 
'email' => $_POST['form']['emailadres']
);
 
header('Location: ' . $exterlink . "?" .  http_build_query($data));