Cookies and Sessions

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What are Cookies and Sessions?

Cookies and Sessions are used to store user data temporarily to maintain state across multiple pages in a web application.

• Cookies store data on the user’s browser

• Sessions store data on the server

Cookies in PHP

What is a Cookie?

A cookie is a small piece of data stored in the user's browser. It is mainly used for user preferences, tracking, and authentication.

Creating a Cookie

setcookie("user", "Admin", time() + 3600, "/");

Accessing a Cookie

echo $_COOKIE['user'];

Deleting a Cookie

setcookie("user", "", time() - 3600, "/");

Cookie Example

if (!isset($_COOKIE['visit'])) {
    setcookie("visit", "1", time() + 3600);
    echo "Welcome, first time visitor!";
} else {
    echo "Welcome back!";
}

Sessions in PHP

What is a Session?

A session stores user data on the server and assigns a unique session ID to the user. This ID is usually stored in a cookie.

Starting a Session

session_start();

Creating Session Variables

$_SESSION['username'] = "Admin";
$_SESSION['role'] = "User";

Accessing Session Variables

echo $_SESSION['username'];

Destroying a Session

session_start();
session_unset();
session_destroy();

Complete Session Example

session_start();

if (!isset($_SESSION['login'])) {
    $_SESSION['login'] = true;
    echo "Session started";
} else {
    echo "Session already exists";
}

Cookies vs Sessions

Security Best Practices

• Use HTTPS for cookies

• Set HttpOnly and Secure flags

• Regenerate session ID after login

• Destroy sessions on logout

• Avoid storing sensitive data in cookies

Secure Cookie Example

setcookie(
    "user",
    "Admin",
    time() + 3600,
    "/",
    "",
    true,
    true
);

Common Use Cases

• Login systems

• Shopping carts

• User preferences

• Authentication and authorization

Conclusion

Cookies and sessions are essential for maintaining user state in PHP applications. Cookies are client-side, while sessions are server-side, making sessions more secure for sensitive data.