不存在会话(Facebook SDK 4）

我制作了一个网站，使用Facebook SDK 4从Facebook页面获取并显示信息。该网站使用WampServer 2.5在localhost上运行良好，但由于我将其上传到了一个免费的托管网站（它运行PHP 5.4），Facebook URL不会返回任何信息，因为没有会话。

有什么想法吗？

<?php
    session_start();// Starting Session
    // storing session
    $user_name = $_SESSION['admin_profile']['username'];
    $user_pass = $_SESSION['admin_profile']['password'];
    // Establishing connection with server by passing server_name, user_id and password as a parameter
    $connection = mysqli_connect('xxx', 'xxx', 'xxx', 'xxx');
    // SQL query to fetch complete information of user
    $ses_sql = mysqli_query($connection, "SELECT * FROM admin WHERE username='$user_name' AND password='$user_pass' ");
    $rows = mysqli_fetch_assoc($ses_sql);
    $login_session = $rows['username'];
    // mysqli_close($connection); // Closing connection
    if(!isset($_SESSION['login_user']))
    {
        mysqli_close($connection); // Closing connection
        header('Location: ../control_panel.php'); // Redirecting to home page
    }
    // Include required files form Facebook SDK
    require_once( '../facebook-php-sdk-v4-4.0-dev/autoload.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/HttpClients/FacebookHttpable.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/HttpClients/FacebookCurl.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/HttpClients/FacebookCurlHttpClient.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/Entities/AccessToken.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/Entities/SignedRequest.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookSession.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookRedirectLoginHelper.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookRequest.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookResponse.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookSDKException.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookRequestException.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookOtherException.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/FacebookAuthorizationException.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/GraphObject.php' );
    require_once( '../facebook-php-sdk-v4-4.0-dev/src/facebook/GraphSessionInfo.php' );
    use Facebook'HttpClients'FacebookHttpable;
    use Facebook'HttpClients'FacebookCurl;
    use Facebook'HttpClients'FacebookCurlHttpClient;
    use Facebook'Entities'AccessToken;
    use Facebook'Entities'SignedRequest;
    use Facebook'FacebookSession;
    use Facebook'FacebookRedirectLoginHelper;
    use Facebook'FacebookRequest;
    use Facebook'FacebookResponse;
    use Facebook'FacebookSDKException;
    use Facebook'FacebookRequestException;
    use Facebook'FacebookOtherException;
    use Facebook'FacebookAuthorizationException;
    use Facebook'GraphObject;
    use Facebook'GraphSessionInfo;
    $db = new mysqli('xxx', 'xxx', 'xxx', 'xxx');
    if (mysqli_connect_errno()) {
         echo "Error: Could not connect to database.  Please try again later.";
         exit;
    }
    $print_result = "";
    $urlErr = "";
    $fb_url = "";
    $url_name = "";
    $url_picture = "";
    $url_link = "";

    /*---------------------Handle submit button----------------------*/
    if ($_SERVER["REQUEST_METHOD"] == "POST") {
        if (empty($_POST["fb_url"])) {
            $urlErr = "S?µp????ste Url";
        }
        else {
            $fb_url = test_input($_POST["fb_url"]);
            $urlErr = "";
        }
    }
    if ($fb_url != ""){
        //INSERT Facebook link into database (Table: facebook_url)
        // Init app with app id and secret
        FacebookSession::setDefaultApplication( 'xxxxx','xxxxx' );

        $session = FacebookSession::newAppSession();
        $accessToken = $session->getAccessToken();
        $session = new FacebookSession($accessToken);
        if ( isset( $_SESSION ) && isset( $_SESSION['$accessToken'] ) ) {
            // Create new session from saved access_token
            $session = new FacebookSession( $_SESSION['$accessToken'] );
            // Validate the access_token to make sure it's still valid
            try {
                if ( !$session->validate() ) {
                    $session = null;
                }
            }
            catch ( Exception $e ) {
                // Catch any exceptions
                $session = null;
            }
        }
        $helper = new FacebookRedirectLoginHelper('http://mevent.gr/control_panel.php');

        if ( !isset( $session ) || $session === null ) {
            // No session exists
            try {
                $session = $helper->getSessionFromRedirect();
            }
            catch( FacebookRequestException $ex ) {
                // When Facebook returns an error
                // handle this better in production code
                print_r( $ex );
            }
            catch( Exception $ex ) {
                // When validation fails or other local issues
                // handle this better in production code
                print_r( $ex );
            }
        }

        if ( isset( $session ) ) {
            // Save the session
            $_SESSION['$accessToken'] = $session->getToken();
            // Create a session using saved token or the new one we generated at login
            $session = new FacebookSession( $session->getToken() );
            try {
                $response = (new FacebookRequest($session, 'GET', "/$fb_url"))->execute();
                $object = $response->getGraphObject();
                $url_id = $object->getProperty('id');
                //Retrieve id of URL
                $request = new FacebookRequest($session, 'GET', "/$url_id/?fields=name,picture,link");
                $response = $request->execute();
                $graphObject = $response->getGraphObject()->asArray();
                //Retrieve name, picture, link
                $url_name = $graphObject['name'];
                $url_picture = $graphObject['picture']->data->url;
                $url_link = $graphObject['link'];

                //INSERT 'url_id', 'fb_url' into table 'facebook_url'
                $url_id = mysqli_real_escape_string($db, $url_id);
                $fb_url = mysqli_real_escape_string($db, $fb_url);
                $query = "INSERT INTO facebook_url (url, id_url) VALUES
                ('$fb_url', '$url_id')";
                $result = $db->query($query);
                if ($result){
                    $print_result = "The facebook url inserted into database";
                }
                else{
                    $print_result = "The facebook url have already inserted into database.";
                }
            }
            catch (FacebookRequestException $ex) {
                //echo $ex->getMessage();
                //echo "Yes_1";
                $urlErr = "Invalid URL";
            }
            catch ('Exception $ex) {
                //echo $ex->getMessage();
                //echo "Yes_2";
                $urlErr = "Invalid URL";
            }
        }
    }
?>

我已经编辑了这个文件。