Gazelle/sections/reports/ajax_add_notes.php

<?php

if (!check_perms('admin_reports') || empty($_POST['id'])) {
  print
    json_encode(
      array(
        'status' => 'failure'
      )
    );
  die();
}

$ID = (int)$_POST['id'];

$Notes = $_POST['notes'];

$DB->query("
  UPDATE reports
  SET Notes = ?
  WHERE ID = ?", $Notes, $ID);
print
  json_encode(
    array(
      'status' => 'success'
    )
  );
die();