The session is lost. What to do?

Question

PHP

Here is the code:

<?php
  session_start();
    $client_id = '51016'; // ID приложения
    $client_secret = 'wTf757oEM4'; // Защищённый ключ
    $redirect_uri = 'http://'; // Адрес сайта

    $url = 'http://oauth.vk.com/authorize';

    $params = array(
        'client_id'     => $client_id,
        'redirect_uri'  => $redirect_uri,
        'response_type' => 'code'
    );

    echo $link = '<p><a href="' . $url . '?' . urldecode(http_build_query($params)) . '">Аутентификация через ВКонтакте</a></p>';

if (isset($_GET['code'])) {
    $result = false;
    $params = array(
        'client_id' => $client_id,
        'client_secret' => $client_secret,
        'code' => $_GET['code'],
        'redirect_uri' => $redirect_uri
    );

    $token = json_decode(file_get_contents('https://oauth.vk.com/access_token' . '?' . urldecode(http_build_query($params))), true);

    if (isset($token['access_token'])) {
        $params = array(
            'uids'         => $token['user_id'],
            'fields'       => 'uid,first_name,last_name,screen_name,sex,bdate,photo_big',
            'access_token' => $token['access_token']
        );

        $userInfo = json_decode(file_get_contents('https://api.vk.com/method/users.get' . '?' . urldecode(http_build_query($params))), true);
        if (isset($userInfo['response'][0]['uid'])) {
            $userInfo = $userInfo['response'][0];
            $result = true; 
        }
    }
   
    if ($result) {
    echo 'Всё ок';
        $_SESSION['user'] = $userInfo;
    }
}	
?>

But the session disappears after reloading the page, what should I do?

Answer 1

put the entire token receiving block into a condition:

if ($_SESSION['user']=='') {
//получаем токен
}