Is there a reason you didn’t just use this?
<select id="animal" name="animal">
<option value="0">--Select Animal--</option>
<option value="Cat">Cat</option>
<option value="Dog">Dog</option>
<option value="Cow">Cow</option>
</select>
if($_POST['submit'] && $_POST['submit'] != 0)
{
$animal=$_POST['animal'];
}