$clientId = 'xxxx';
$clientSecret = 'xxxx';
$client = new OAuth2\Client($clientId, $clientSecret);

$client->setAccessToken('xxxx');

$baseApiUrl = 'https://atlanticsunrise.nationbuilder.com';

$data = array (
    'person' => array (
        'first_name' => 'jake',
        'last_name' => 'Doe',
            'email' => 'fake3@email.com'
    )
);

$response = $client->fetch( $baseApiUrl ."/api/v1/people" , $data, 'POST');

echo '<pre>';
print_r($response);
echo '</pre>';