Laravel OAuth 2.0 Authentication using Guzzle Client - php

Question

I am developing an application like Postman Client in Laravel. For that, I am using Guzzle Client.
For OAuth 2.0 authentication, I have used the below link as reference,
Reference Link
I have tried the below code,
$token_storage = new FileTokenPersistence('/tmp/token.txt');
$baseurl="https://api.tradegecko.com/oauth/token";
$auth_code="";
$client_id="MYCLIENTID";
$client_secret="MYSECRET";
$redirect_uri="http://localhost:81/postman/public/request/instantadd";
if ($token_storage->hasToken() === false) {
$auth_url = 'https://api.tradegecko.com/oauth/authorize?'.http_build_query([
'client_id' => $client_id,
'redirect_uri' => $redirect_uri,
'response_type' => 'code',
'prompt' => 'select_account',
'scope' => '',
'access_type' => 'offline',
]);
echo "Go to the following link in your browser:\n\n";
echo " $auth_url\n\n";
// if(! defined('STDIN')) define('STDIN', fopen("php://stdin","r"));
echo "Enter verification code: ";
$auth_code = trim(fgets(STDIN, 1024));
}
$reauth_client = new \GuzzleHttp\Client(['verify' => 'E:\cacert.pem',
'base_uri' => $baseurl,
]);
$reauth_config = [
'code' => $auth_code,
'client_id' => $client_id,
'client_secret' => $client_secret,
'redirect_uri' => $redirect_uri,
];
$grant_type = new AuthorizationCode($reauth_client, $reauth_config);
$refresh_grant_type = new RefreshToken($reauth_client, $reauth_config);
$oauth = new OAuth2Middleware($grant_type, $refresh_grant_type);
$oauth->setTokenPersistence($token_storage);
$stack = HandlerStack::create();
$stack->push($oauth);
$client = new \GuzzleHttp\Client(['verify' => 'E:\cacert.pem',
'handler' => $stack,
'auth' => 'oauth',
]);
$response = $client->get($requesturl, $options);
$result=json_decode($response->getBody(),true);
I am getting an error in auth code retrieving. When I go to the authurl link, I am getting the token.
The error I am getting is:
"message": "Unable to request a new access token"
Also, I don't know what is the use of STDIN.....How can I put the auth code here?
Please help me.
Regards,Rekha