gistfile1.php

<?php
require('PHP-OAuth2/src/OAuth2/Client.php');
require('PHP-OAuth2/src/OAuth2/GrantType/IGrantType.php');
require('PHP-OAuth2/src/OAuth2/GrantType/AuthorizationCode.php');


$clientId = '9b8b0e1fe97d8efb3cb634ea65c03c8de269121894b980b1935db889aac11634';
$clientSecret = 'afc5c60f67b00443d858efb9226b71da3a64873764ae4acf7d4a8cfc43cff91c';
$client = new OAuth2\Client($clientId, $clientSecret);

$client->setCurlOption(CURLOPT_SSL_VERIFYPEER, true);

#NOTE: SET THE BELOW TO THE CODE YOU GET FROM THE CALLBACK
$code = 'd80bd609b7634d77fb6f38a444cfb093da6c596c98b49fc0099ff8864e30d8b8';
$redirectUrl    = 'http://www.example.com/oauth_callback';

  
// generate a token response
$accessTokenUrl = 'https://arion.nationbuilder.com/oauth/token';
$params = array('code' => $code, 'redirect_uri' => $redirectUrl);
$response = $client->getAccessToken($accessTokenUrl, 'authorization_code', $params);

// set the client token
$token = $response['result']['access_token'];
$client->setAccessToken($token);

$baseApiUrl = 'https://arion.nationbuilder.com';
$client->setAccessToken($token);
$response = $client->fetch($baseApiUrl . '/api/v1/people');
print_r($response);
?>