how do sessions work in php code example

Example: php sessions

<?php
  	// Start new or resume existing session.
  	session_start();
	
	// Add values to the session.
	$_SESSION['item_name'] = 'value'; // string
	$_SESSION['item_name'] = 0; // int
	$_SESSION['item_name'] = 0.0; // float

	// Get session values.
	$value = $_SESSION['item_name'];
?>