logout.php

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Notice</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" />
    <link rel="preconnect" href="https://fonts.gstatic.com" />
    <link href="https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;500;600;700&display=swap" rel="stylesheet" />
    <link rel="stylesheet" href="style/reset.css" />
    <link rel="stylesheet" href="style/style.css" />
</head>
<body>
    <?php
        session_start();
        unset($_SESSION['current_user']); // facebook
        unset($_SESSION['access_token']); // google
    ?>
    <div class="box-content">
        <h1>Successful sign out</h1>
        <a href="index.php">back to sign in page</a>
    </div>
</body>
</html>