Destroy PHP Sessions on Browsers Tab Close

i am stucked, i am working on Projects hotbartendersla

i have used a lot of sessions to process data in event booking, now i want to destroy the session when user closed the window/tab of browser,because when ever i open site the selection remains same as i did.

i have used this

<script type="text/javascript">
  window.onbeforeunload = function() {

    $.post("mysessionsdestroypage.php",function(data){
    });  

  }
</script>

but when i jumped to on step 2,step 3, my sessions are destroyed and data don't reached on step 4. i searched alot but i found no reliable solution for this

First of all Set Session time out on the page where you want to clear Sessions

<?php
// destroy session in 15 minutes, 900 ms =15 minutes

if (isset($_SESSION['LAST_ACTIVITY_step1']) && (time() -   $_SESSION['LAST_ACTIVITY_step1'] > 900)) {

 header("Location:http://www.hotbartendersla.com/session-destroy");
 }
 $_SESSION['LAST_ACTIVITY_step1'] = time(); // the start of the session.

?>

Then make a new page(in wordpress) to destroy sessions and add template to that page,

pagedestroy-sessions.php

<?php
/*
Template Name: Destroy Sessions
*/
session_start();

include('header.php');


 session_destroy();
 session_unset();
 ?>
 <h2>Session Has Been Destroyed </h2>
<?php
include('footer.php');
?>

<script type="text/javascript">
function redirect() {
  document.location = 'https://www.hotbartendersla.com/event-booking-step-1';
}
  <!- after 1 second redirect to event-booking-step-1 Page-->
  setTimeout(redirect(),1000);

</script>