What is $_SESSION In PHP

$_SESSION is a built-in PHP superglobal variable that is used to store and retrieve session data across different pages on a website.

A session is a way for a server to remember information about a user between HTTP requests. When a user logs in to a website, for example, the server can create a unique session ID and store it in a cookie on the user’s computer. This session ID can then be used to track the user’s activity on the website, such as their shopping cart contents, their login status, or any other information that needs to be persisted across multiple pages.

$_SESSION is an associative array that contains key-value pairs of session data. To store data in the session, you simply assign a value to a key in the $_SESSION array, like this:

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

To retrieve data from the session, you simply access the key in the $_SESSION array, like this:

echo 'Welcome back, ' . $_SESSION['username'];

The $_SESSION variable is available on any page that has session support enabled, which is typically done by calling the session_start() function at the beginning of the PHP code. This function initializes a new session or resumes an existing session, depending on whether a session ID cookie is present.

It’s important to note that session data is stored on the server, not on the user’s computer, and can be destroyed by the server or by the user logging out or closing their browser. Additionally, session data is vulnerable to various security threats, such as session hijacking or cross-site scripting (XSS) attacks, so it’s important to use best practices for session management and security.