问私有API创建标准-这个API正确吗？

EN

class Api
{
    /**
     * Default function called when API url is accessed
     *
     * @return mixed
     * @throws Exception
     */
    public function index()
    {
        $appId = isset($_GET['appId']) ? $_GET['appId'] : null;
        $apiKey = $_GET['apiKey'] ? $_GET['apiKey'] : null;
        $method = $_GET['use'] ? $_GET['use'] : null;

        $data = json_decode(file_get_contents("php://input"), true);

        if ($this->validateRequest($appId, $apiKey, $method)) {
            return call_user_func_array(array($this, $method), array($data));
        }
    }

    private function validateRequest($appId, $apiKey, $method)
    {
        # check referer
        $requestUri = isset($_SERVER["HTTP_REFERER"]) ? $_SERVER["HTTP_REFERER"] : null;

        if (!$requestUri) {
            $this->bye('HTTP_REFERER is required!');
        }

        # check if method exists
        if (!$method || !method_exists('Apicall', $method)) {
            $this->bye('Invalid \'use\' value!');
        }

        # check appId, apiKey and requestUri
        if (!$appId) {
            $this->bye('Invalid appId!');
        }

        if (!$apiKey) {
            $this->bye('Invalid apiKey!');
        }

        $db = new DB();
        $db->where('appid', $appId);
        $db->where('apikey', $apiKey);
        $db->where('request_uri', pathWithoutEndingSlash($requestUri));
        $db->get();

        if ($db->exists() && $db->result_count() > 0) {
            return true;
        }

        $this->bye('Request Denied!');
    }

    private function bye($error)
    {
        echo json_encode(array('Error' => $error));
        exit;
    }

    private function getIntervals()
    {
        $values = array('monthly', 'quarterly', 'yearly', 'single_payment');
        echo json_encode($values);
    }
}