how does php session work code example

Example 1: destroy session php

<?php 
 session_start(); // start session
 session_destroy();  // Delete whole session
// OR
unset($_SESSION['username']); // delete any specific session only
?>

Example 2: create session in php

<?php 
  // Start the session
  session_start();

  // Set session variables
  $_SESSION["color"]= "blue";
  $_SESSION["animal"]= "dog";
  echo "The session variable are set up.";
?>