Sessions & Cookies in PHP
From the PHP cheat sheet · Web Features · verified Jul 2026
Sessions & Cookies
Managing user sessions and cookies
php
// Sessions
session_start();
$_SESSION['user_id'] = 123;
$_SESSION['username'] = 'john';
// Check session
if (isset($_SESSION['user_id'])) {
// User is logged in
}
// Cookies
setcookie('name', 'value', time() + 3600);
$value = $_COOKIE['name'] ?? null;
// Headers
header('Content-Type: application/json');
header('Location: /dashboard');💡 session_start() must be called before any output
⚡ Use secure, httponly, and samesite for cookie security
📌 Always exit() after header redirects
🔥 Regenerate session ID after login to prevent fixation
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