<?php
  if (isset($_POST["submit"])) {
    if ($_POST["category"] == 1 || $_POST["category"] == 2) {
      setcookie("category", $_POST["category"], time() + (60 * 60 * 24 * 30));
    }
  }
?>
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>PHP Document</title>
</head>
<body>
  <section>
    <form name="myform" method="post" action="index.php">
      <input type="text" name="myname">
      <select name="category">
        <option value="1" selected>Fiction</option>
        <option value="2">Non-Fiction</option>
      </select>
      <input type="submit" name="submit">
    </form>
  </section>
</body>
</html>