Error with Select

<div class="container">
           <form action="test.php" method="POST" name="cartype">
            <section class="mt-3">
                <select class="mdb-select">
                    <option value="" disabled selected>Choose your option</option>
                    <option value="1">Option 1</option>
                    <option value="2">Option 2</option>
                    <option value="3">Option 3</option>
                </select>
                <label>Example label</label>
            </section>

            <input type="submit" value="submit" class="btn btn-success" />

           </form>
        </div>


and the PHP code:

<?php

if (isset($_POST['cartype']))
{
    $optionSelected = $_POST['cartype'];
    echo $optionSelected;
}