how to use start session() once php code example

Example 1: 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.";
?>

Example 2: session start php

<?php
// This sends a persistent cookie that lasts a day.
session_start([
    'cookie_lifetime' => 86400,
]);
?>