Session and Cookies in PHP: When to Use What?

Both Sessions and Cookies are used to store user data, but they differ in how and where the data is stored. When developing web applications, managing user data efficiently is crucial. Two common ways to store user-related data in PHP are sessions and cookies. While both methods maintain user state, they work differently and are suited for different use cases. In this article, we will explore the differences between both in PHP and discuss when to use each with practical examples.

What is a Cookie?

A cookie is a small data stored on the user’s browser. It allows websites to remember user preferences, login information, and other details across multiple visits.

Setting a Cookie in PHP:

// Set a cookie that expires in 1 hour
setcookie("user", "JohnDoe", time() + 3600, "/");

Retrieving a Cookie:

if(isset($_COOKIE["user"])) {
    echo "Welcome back, " . $_COOKIE["user"];
} else {
    echo "Hello, Guest!";
}

When to Use Cookies?

1)When data needs to persist across multiple visits.
3)For storing user preferences and settings.
4)When small amounts of non-sensitive data need to be retained.

What is a Session?

A session is a temporary storage mechanism that holds user data on the server. Unlike cookies, session data is not stored in the browser and is automatically deleted when the user closes the browser or the session expires.

Starting a Session & Storing Data:

<?php
session_start();
$_SESSION["username"] = "JohnDoe";
?>

Retrieving Session Data:

<?php
session_start();
if(isset($_SESSION["username"])) {
    echo "Hello, " . $_SESSION["username"];
} else {
    echo "Please log in.";
}

?>

When to Use Sessions?

1)When handling sensitive information like login credentials.
2)To track user activity during a single visit.
3)When storing large amounts of temporary data.

Differences Between Sessions & Cookies in PHP

1)Storage:

Cookies store data on the client-side (browser), while sessions store it on the server-side for better security.

2)Lifetime:

Cookies persist until their expiry time, whereas sessions last only until the user closes the browser or logs out.

3)Security:

Sessions are more secure since data is not exposed to the user, unlike cookies, which can be accessed and modified.

4)Data Size:

Cookies have a 4KB limit, while sessions can store larger amounts of data on the server.

Conclusion

Both have their use cases in PHP applications. Use cookies for storing non-sensitive user preferences and sessions for managing secure, temporary user data. Understanding their differences will help you decide which method best fits your application’s needs.