OpenTok | 未找到令牌生成类“角色”

I am getting this error whenever i am trying to generate token Fatal error: Class 'Role' not found in..

May be i am missing any dependency.

config.php

<?php 
   require_once('vendor/autoload.php');
   use OpenTok\OpenTok;
   use OpenTok\Session;
   use OpenTok\Role;
   $key= 123455;
   $secret='87643gri8y98643kjg49874';
   $present_session ='jhvh5489754kb54089u43r398y5';
   $opentok = new OpenTok($key,$secret);
 ?>

getToken.php

<?php 
include('config.php');

$token = $opentok->generateToken('pjijirtolnpjr', array(
        'data' => json_encode(array( 
            'name' => 'oihohtr'
        )),
        'role' => Role::SUBSCRIBER
    ));


echo  $token;

?>

app.js

$(document).ready(function(){

    var presenceSession = OT.initSession(45319022, '1_MX40NTMxOTAyMn5-MTQ0MTYyMzM3ODg2Mn4zTHBxOUZKOFBhdzc1bnk0OEVvMlozY3h-UH4');

    if(presenceSession.sessionId){

        $.get('getToken.php',function(data,status){

            console.log(data);

        });
    }
});

Try this

<?php 
include('config.php');
use OpenTok\Session;
use OpenTok\Role;

$token = $opentok->generateToken('pjijirtolnpjr', array(
        'data' => json_encode(array( 
            'name' => 'oihohtr'
        )),
        'role' => Role::SUBSCRIBER
    ));


echo  $token;

?>

Refer documentation