PHP — Cookies

Setting cookies

<?php
// Set cookie (must be before any output)
setcookie('username', 'Alice', time() + 3600, '/');
setcookie('theme', 'dark', time() + 86400, '/', '.example.com', true, true);

// Set with parameters
setcookie(
    'user_prefs',
    json_encode(['lang' => 'en', 'theme' => 'dark']),
    time() + 30 * 24 * 60 * 60, // 30 days
    '/',
    '',
    false,
    true
);
?>

Reading cookies

<?php
if (isset($_COOKIE['username'])) {
    echo "Welcome, " . $_COOKIE['username'];
}

// Parse JSON cookie
if (isset($_COOKIE['user_prefs'])) {
    $prefs = json_decode($_COOKIE['user_prefs'], true);
    echo "Language: " . $prefs['lang'];
}
?>

Deleting cookies

<?php
// Set expiration in the past
setcookie('username', '', time() - 3600, '/');
unset($_COOKIE['username']);
?>

Cookie security

<?php
setcookie('token', $value, [
    'expires' => time() + 3600,
    'path' => '/',
    'domain' => 'example.com',
    'secure' => true,    // HTTPS only
    'httponly' => true,  // No JavaScript access
    'samesite' => 'Strict'
]);
?>

Sessions vs cookies

Feature	Sessions	Cookies
Storage	Server	Browser
Size	Unlimited	4KB
Security	More secure	Less secure
Lifetime	Until browser closes	Configurable
Use case	Login state	Preferences

Mini Practice

Write PHP code that:

1. Sets a cookie with expiration
2. Reads a cookie value
3. Deletes a cookie
4. Compares sessions and cookies

Up Next

In the next lesson, you'll learn about Forms — processing HTML forms.