PHP添加下拉值以更新记录

I have users being selected by PE value and returns its record. I want to be able to add a dropdown in the form to select I know how to do it in HTML but how do i go it when I am POST "id" to 'id' Add a drop down for PE so they can select a range.

if (isset($_POST['submit'])) {
  try {
    $connection = new PDO($dsn, $username, $password, $options);
    $MyGuests =[
      "id"        => $_POST['id'],
      "firstname" => $_POST['firstname'],
      "lastname"  => $_POST['lastname'],
      "email"     => $_POST['email'],
      "PE"       => $_POST['PE'],
      "Department"  => $_POST['Department'],
      "senority"      => $_POST['senority']
    ];

   $sql = "UPDATE MyGuests 
        SET id = :id,