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Sessions and Cookies

 

In PHP, sessions and cookies are used to store data across multiple pages. While both serve the purpose of remembering user information, they differ in how and where the data is stored.

PHP Sessions

What is a Session?

A session is a way to store information (variables) to be used across multiple pages. The data is stored on the server, and only a unique session ID is stored in the user’s browser.

Starting a Session

<?php
session_start(); // Must be at the top of the page
 
$_SESSION["username"] = "JohnDoe";
echo "Session is set for user: " . $_SESSION["username"];
?>

Accessing Session Data

<?php
session_start();
echo "Welcome back, " . $_SESSION["username"];
?>

Destroying a Session

<?php
session_start();
session_unset(); // Remove session variables
session_destroy(); // Destroy the session
?>

PHP Cookies

What is a Cookie?

A cookie is a small file stored on the user’s browser. Cookies are used to remember information such as user preferences or login status. The data is stored client-side.

Setting a Cookie

<?php
setcookie("user", "JohnDoe", time() + (86400 * 7), "/");
// Cookie expires in 7 days
?>

Accessing a Cookie

<?php
if (isset($_COOKIE["user"])) {
    echo "Welcome back, " . $_COOKIE["user"];
} else {
    echo "User cookie not set.";
}
?>

Deleting a Cookie

<?php
setcookie("user", "", time() - 3600, "/"); // Expire in the past
?>

Sessions vs Cookies

Feature

Sessions (Server-side)

Cookies (Client-side)

Storage

Stored on the server

Stored in the browser

Security

More secure (data not visible to user)

Less secure (data visible in browser)

Capacity

Large (depends on server)

Limited (~4KB)

Use Case

Login systems, shopping carts

User preferences, remembering settings

 

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