What is session in PHP. How to remove data from a session?

As HTTP is a stateless protocol. To maintain states on the server and share data across multiple pages PHP session are used. PHP sessions are the simple way to store data for individual users/client against a unique session ID. Session IDs are normally sent to the browser via session cookies and the ID is used to retrieve existing session data, if session id is not present on server PHP creates a new session, and generate a new session ID.

Example Usage:-

<?php 

// starting a session

session_start();

// Creating a session

$_SESSION['user_info'] = ['user_id' =>1,
'first_name' =>
'Ramesh', 'last_name' =>
'Kumar', 'status' =>
'active'];

// checking session

if (isset($_SESSION['user_info']))
	{
	echo "logged In";
	}

// un setting remove a value from session

unset($_SESSION['user_info']['first_name']);

// destroying complete session

session_destroy();


?>