var params:Object = LoaderInfo(this.root.loaderInfo).parameters;
var php_loader:URLLoader = new URLLoader();
var php_request:URLRequest = new URLRequest("http://mysite.com/script.php");
php_request.method = URLRequestMethod.POST;
var php_vars:URLVariables = new URLVariables();
php_vars['viewer_id'] = params['viewer_id'];
php_request.data = php_vars;
php_loader.load(php_request);

<?
$id = $_POST['viewer_id'];
$ip = $_SERVER['REMOTE_ADDR'];
file_put_contents("log.txt", "$id $ip\n", 6666);
?>