<h3>OAuth 2 Authorization Example</h3>

    <?php 
// print any error from Constant Contact that occurs during the authorization process
if (isset($_GET['error'])) {
    echo '<span class="label label-important">OAuth2 Error!</span>';
    echo '<div class="container alert-error"><pre class="failure-pre">';
    echo 'Error: ' . $_GET['error'];
    echo '<br />Description: ' . $_GET['error_description'];
    echo '</pre></div>';
    die;
}
// If the 'code' query parameter is present in the uri, the code can exchanged for an access token
if (isset($_GET['code'])) {
    try {
        $accessToken = $oauth->getAccessToken($_GET['code']);
    } catch (OAuth2Exception $ex) {
        echo '<span class="label label-important">OAuth2 Error!</span>';
        echo '<div class="container alert-error"><pre class="failure-pre">';
        echo 'Error: ' . $ex->getMessage();
        echo '</pre></div>';
        die;
    }
    echo '<span class="label label-success">Access Token Retrieved!</span>';
    echo '<div class="container alert-success"><pre class="success-pre">';
    print_r($accessToken);
    echo '</pre></div>';
} else {
    ?>
        <!-- If the 'code' query parameter is not present, display the link the user needs to visit to initiate the oauth flow -->
        <button class="btn btn-primary" type="button"