Sessions & Cookies Management

State management in PHP divides data storage between client and server:

• Cookies: Data stored directly on the client's browser (e.g. tracking identifiers). Set using the `setcookie()` function. They are sent to the server automatically with every page request.
• Sessions: Secure data stored on the web server (e.g. login credentials). Initiated using the **`session_start()`** function at the very top of the script. Values are stored inside the `$_SESSION` superglobal array.

Let's look at an example initializing sessions and setting cookies:

<?php
// Start the session (must be the first line of the script)
session_start();

// Store data in session
$_SESSION['user_id'] = 405;
$_SESSION['role'] = "Administrator";

echo "Session Started! User ID: " . $_SESSION['user_id'] . "\n";

// Set a cookie (expires in 1 hour)
setcookie("theme", "dark", time() + 3600, "/");
echo "Theme Cookie initialized.\n";
?>