PHP Superglobals: Session

Introduction

PHP Superglobals are built-in variables that are always accessible, regardless of scope. One important superglobal is the $_SESSION array, which is used to manage session variables in PHP.

Key Concepts

What is a Session?

• A session is a way to store information (variables) to be used across multiple pages.
• It allows you to maintain state in a stateless HTTP environment.

How Sessions Work

• When a user visits a website, PHP creates a unique session ID and saves it on the server.
• The session ID is passed between the server and client (usually through cookies) to maintain the user's state.

Using $_SESSION

Starting a Session

To use sessions, you must start the session at the beginning of your PHP script using session_start().

<?php
session_start();
?>

Storing Data in Sessions

You can store data in the $_SESSION array as follows:

$_SESSION['username'] = 'JohnDoe';
$_SESSION['email'] = '[email protected]';

Accessing Session Data

You can access the session variables on any page after starting the session:

echo $_SESSION['username']; // Outputs: JohnDoe

Modifying Session Data

You can update the session variable just like any other variable:

$_SESSION['email'] = '[email protected]';

Destroying a Session

To remove all session variables and destroy the session, you can use:

session_unset(); // Unset all session variables
session_destroy(); // Destroy the session

Example

Here is a simple example that demonstrates starting a session, storing, and accessing session data:

page1.php

<?php
session_start();
$_SESSION['username'] = 'JohnDoe';
echo "Session is set.";
?>

page2.php

<?php
session_start();
echo "Welcome, " . $_SESSION['username']; // Outputs: Welcome, JohnDoe
?>

Conclusion

• Sessions are a powerful feature in PHP that allows you to keep track of user data across different pages.
• By using the $_SESSION superglobal, you can easily manage user-specific data throughout their visit to your website.

This summary provides a basic understanding of PHP sessions and how to implement them in a simple way for beginners.