You started your session, then you asked if it is a post request or not.
Then you checked if that post variable isset() to start your code.
Unfortunately the code never run and you have no idea what happened.
Add the 2 lines in red in the following code to find out which post variables exist.

 

<?php
session_start();
if ($_SERVER[‘REQUEST_METHOD’] == ‘POST’)
{

  // the 2 lines for your debug
foreach ($_POST as $key => $value)
       echo «Field «.$key.» is «. htmlspecialchars($value).»<br>»;
 
if (isset($_POST[«customer_id»]))
{

          // Your code

 }

}

?>