Sessions
Sessions store user data on the server across multiple page requests. Each user gets a unique session ID stored in a cookie.
Example
<?php
// Start session (must be called before any output)
session_start();
// Set session data
$_SESSION['user'] = 'Alice';
$_SESSION['role'] = 'admin';
$_SESSION['login_time'] = time();
// Read session data
if (isset($_SESSION['user'])) {
echo "Welcome, " . $_SESSION['user'];
}
// Remove specific session variable
unset($_SESSION['role']);
// Destroy entire session (logout)
session_destroy();
?>Cookies
Cookies are stored on the user's browser and sent with every request. Use them for preferences and non-sensitive data.
Example
<?php
// Set a cookie (expires in 30 days)
setcookie('theme', 'dark', time() + (86400 * 30), '/');
setcookie('language', 'en', time() + (86400 * 30), '/');
// Read cookies
$theme = $_COOKIE['theme'] ?? 'light';
echo "Theme: $theme";
// Delete a cookie (set expiration in the past)
setcookie('theme', '', time() - 3600, '/');
// Check if cookies are enabled
if (count($_COOKIE) > 0) {
echo "Cookies are enabled";
}
?>