Laravel 4 API不允许来自外部站点的POST请求

我正试图通过从外部站点向我的Laravel 4 API发出POST请求来创建一个用户。我已经将以下代码添加到我的app/filters.php文件中：

App::before(function($request)
{
    if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
        header('Access-Control-Allow-Origin', 'http://www.myexternalsite.net');
        header('Allow', 'GET, POST, OPTIONS, PUT, DELETE');
        header('Access-Control-Allow-Headers', 'Origin, Content-Type, Accept, Authorization, X-Request-With');
        header('Access-Control-Allow-Credentials', 'true');
        exit;
    }
});
App::after(function($request, $response)
{
    $response->headers->set('Access-Control-Allow-Origin', 'http://www.myexternalsite.net');
    $response->headers->set('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
    $response->headers->set('Access-Control-Allow-Headers', 'Origin, Content-Type, Accept, Authorization, X-Requested-With');
    $response->headers->set('Access-Control-Allow-Credentials', 'true');
    $response->headers->set('Access-Control-Max-Age','86400');
    return $response;
});

当我在来自的POST请求上运行我的开发工具时http://www.myexternalsite.net我收到以下警告信息：

event.returnValue is deprecated. Please use the standard event.preventDefault() instead. main-built.js:6

以及以下错误消息：

OPTIONS http://api.mywebsite.com/users 500 (Internal Server Error) main-built.js:7
OPTIONS http://api.mywebsite.com/users No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://www.myexternalsite.net' is therefore not allowed access. main-built.js:7

我是不是错过了什么？