Alternative to layerhq/layer-identity-token-php that works on Laravel 4.2

AuthController.php

<?php

use Namshi\JOSE\JWS;

class AuthController extends Controller {

  function layer_identity_token() {

    if (Auth::user()->id !== Input::get('user_id')) {
      App::abort(500);
    }

    $jws = new JWS('JWT');

    $jws->setHeader([
      'typ' => 'JWT',
      'alg' => 'RS256',
      'cty' => 'layer-eit;v=1',
      'kid' => Config::get('services.layer.private_key_id')
    ]);

    $jws->setPayload([
      'iss' => Config::get('services.layer.provider_id'),
      'prn' => (string) Auth::user()->id,
      'iat' => (int) Carbon::now()->format('U'),
      'exp' => (int) Carbon::now()->addMinutes(5)->format('U'),
      'nce' => Input::get('nonce'),
      'display_name' => Auth::user()->account->name
    ]);

    $privateKey = openssl_pkey_get_private(Config::get('services.layer.private_key'));
    $jws->sign($privateKey);

    return [
      'identity_token' => $jws->getTokenString()
    ];

  }
}