GraphQL Client For PHP Using Guzzle

example.php

<?php

$endPoint = 'https://api.github.com/graphql';

$query = <<<'GRAPHQL'
query getUsers {
  user {
    id
    name
  }
}
GRAPHQL;

graphqlQuery($endPoint, $query, 'oauth-token');
                 

graphql-client.php

<?php

function graphqlQuery($endPoint, $query, $accessToken);
{
 $response = new Client([
      'base_uri' => $endPoint,
      'headers' => [
          'Authorization' => 'Bearer '.$accessToken,
          'Content-Type' => 'application/json',
      ],
      'body' => json_encode([
          'query' => $query,
      ]),
  ]);

  return new ArrayCollection(json_decode($response->getBody()->getContents(), true));
}

So how do i pass variables to my Query