how to get dutchie graphQL api working with php

I am working to get response from dutchie GrapghQL api using PHP, These are working fine with POSTMAN , but when I am trying to get them work with below Library , its not working at all, and there is very less documentation available for dutchie(php graghql)

https://github.com/webonyx/graphql-php/

Before I have worked on rest apis with php MySQL, its totally new thing to me so not getting how get it work

Postman working image

 <?php
 include("library/graphQL/vendor/autoload.php");

 use GraphQL\Client;
 use GraphQL\Exception\QueryError;


 $client = new Client(
'https://plus.dutchie.com/plus/2021-07/graphql',
["Authorization" => "public-  eyJhbGciOiJIUzI1NiJ9."]
 );

// Create the GraphQL mutation
 $gql = (new Mutation('Ping'))
 ->setSelectionSet(
    [
        'id',
        'time',
    ]
);

 // Run query to get results
 try {
$results = $client->runQuery($gql);
 }
 catch (QueryError $exception) {

// Catch query error and desplay error details
print_r($exception->getErrorDetails());
exit;
}

 Display original response from endpoint
 var_dump($results->getResponseObject());

 Display part of the returned results of the object
 var_dump($results->getData()->pokemon);

 Reformat the results to an array and get the results of part of the array
 $results->reformatResults(true);
 print_r($results->getData()['data']);

Error I am getting

  Fatal error: Uncaught Error: Class 'Mutation' not found in 
  C:\xampp\htdocs\dispoapi\index.php:21 Stack trace: #0 {main} 
  thrown in C:\xampp\htdocs\dispoapi\index.php on line 21