How can session variables impact user login/logout functionality in PHP?

Session variables play a crucial role in maintaining user login/logout functionality in PHP. When a user logs in, their unique session ID is stored in a session variable, allowing the server to identify and authenticate the user for subsequent requests. When a user logs out, the session variable containing their ID is unset, effectively ending their authenticated session. 

// Start the session
session_start();

// Check if the user is logged in
if(isset($_SESSION['user_id'])) {
    // User is logged in, perform logout actions
    unset($_SESSION['user_id']);
    // Redirect to login page or any other desired page
    header("Location: login.php");
    exit();
} else {
    // User is not logged in, redirect to login page
    header("Location: login.php");
    exit();
}

Keywords

Session variables user login user logout PHP functionality error handling

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