A PHP application to demonstrate authenticating with the Campaign Monitor API using OAuth. Uses the createsend-php library as well as the Slim PHP micro framework (but could easily be adapted for use with any PHP framework).

createsend-oauth.php

<?php
# 1. Ensure you have Slim installed and in your include path.
# 2. Ensure you have createsend-php installed and in your include path.
# 3. Set CREATESEND_CLIENT_ID, CREATESEND_CLIENT_SECRET, 
#    and CREATESEND_REDIRECT_URI environment variables for
#    your registered OAuth application.

require 'createsend/csrest_general.php';
require 'Slim/Slim.php';
\Slim\Slim::registerAutoloader();
$app = new \Slim\Slim();

$app->get('/', function () use ($app) {
    $authorize_url = CS_REST_General::authorize_url(
        getenv('CREATESEND_CLIENT_ID'),
        getenv('CREATESEND_REDIRECT_URI'),
        'ViewReports,CreateCampaigns,SendCampaigns');
    $app->redirect($authorize_url);
});

$app->get('/exchange_token', function () use ($app) {
    $code = $app->request()->params('code');
    $result = CS_REST_General::exchange_token(
        getenv('CREATESEND_CLIENT_ID'),
        getenv('CREATESEND_CLIENT_SECRET'),
        getenv('CREATESEND_REDIRECT_URI'),
        $code
    );

    if ($result->was_successful()) {
        $access_token = $result->response->access_token;
        $expires_in = $result->response->expires_in;
        $refresh_token = $result->response->refresh_token;

        $response = "<pre>";
        $response .= "Your user is successfully authenticated. Here are the details you need:<br/><br/>";
        $response .= "access token: ".$access_token."<br/>";
        $response .= "refresh token: ".$refresh_token."<br/>";
        $response .= "expires in: ".$expires_in."<br/>";
        $response .= "<br/><br/>";

        $auth = array(
          'access_token' => $access_token,
          'refresh_token' => $refresh_token
        );
        $cs = new CS_REST_General($auth);
        $clients = $cs->get_clients()->response;

        $response .= "We've made an API call too. Here are your clients:<br/><br/>";
        $response .= var_export($clients, true);
        $response .= "</pre>";

    } else {
        $response = 'An error occurred:<br/>';
        $response .= $result->response->error.': '.$result->response->error_description."<br/>";
    }
    echo $response;
});

$app->run();

where include that file in the wordpress project