Oauth for DeviantArt

deviantOauth.php

<?php
//Relies on the oAuth2 library by Pierrick Charron: https://github.com/adoy/PHP-OAuth2/

const CLIENT_ID = '***'; // OAuth 2.0 client_id
const CLIENT_SECRET = '***'; // OAuth 2.0 client_secret

const REDIRECT_URI = 'http://getcoolphoto.com/site/deviant';
const AUTHORIZATION_ENDPOINT = 'https://www.deviantart.com/oauth2/draft15/authorize';
const TOKEN_ENDPOINT = 'https://www.deviantart.com/oauth2/draft15/token';
const SUBMIT_API = "http://www.deviantart.com/api/draft15/stash/submit";
const APPNAME = 'getcoolphoto';
if (empty($_SESSION['deviant_access_token'])) {
    Yii::import('application.components.OAuth2.*');
    require('Client.php');

    Yii::import('application.components.OAuth2.GrantType.*');
    require('IGrantType.php');
    require('ClientCredentials.php');
    require('Password.php');
    require('RefreshToken.php');
    require('AuthorizationCode.php');

    try {
        $client = new OAuth2\Client(CLIENT_ID, CLIENT_SECRET, OAuth2\Client::AUTH_TYPE_AUTHORIZATION_BASIC);
        if (!isset($_REQUEST['code'])) {
            $params = array('redirect_uri' => REDIRECT_URI);
            $auth_url = $client->getAuthenticationUrl(AUTHORIZATION_ENDPOINT, REDIRECT_URI);
            header('Location: ' . $auth_url);
            die('Redirecting ...');
        } else {
            $params = array('code' => $_REQUEST['code'], 'redirect_uri' => REDIRECT_URI);
            $response = $client->getAccessToken(TOKEN_ENDPOINT, OAuth2\Client::GRANT_TYPE_AUTH_CODE, $params);
            $val = $response['result'];

            if (!$val) {
                throw new Exception('No valid JSON response returned');
            }

            if (!$val['access_token']) {
                throw new Exception("No access token returned: ".$val['human_error']);
            }

            $client->setAccessToken($val['access_token']);

            $client->setAccessTokenType(OAuth2\Client::ACCESS_TOKEN_OAUTH);

            $_SESSION['deviant_access_token'] = $val['access_token'];
            $this->redirect('/site/deviant');
        }
    } catch (Exception $e) {
        print "Fatal Error: ".$e->getMessage();
    }
} else {
?>
    <form action="https://www.deviantart.com/api/draft15/stash/submit?access_token=<?php echo $_SESSION['deviant_access_token']; ?>" method="POST" enctype="multipart/form-data">
        <input type="file" name="photo">
        <input type="submit" value="GO">
    </form>
<?php
}
?>