select2 kullanabilirsiniz.
örnek:
<html>
<head>
<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.min.css" rel="stylesheet" />
</head>
<body>
<?php
if(isset($_POST['dropdown-submit'])){
echo 'seçilen değer: '.$_POST['dropdown'];
}
?>
<form method="post" action="#">
<select class="select2" tabindex="-1" aria-hidden="true" name="dropdown">
<option>Alabama</option>
<option selected>Alaska</option>
<option>California</option>
<option>Delaware</option>
<option>Tennessee</option>
<option>Texas</option>
<option>Washington</option>
</select>
<input type="submit" name="dropdown-submit" value="gönder" />
</form>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js"></script>
<script>
$(document).ready(function() {
$('.select2').select2();
});
</script>
</body>
</html>
verdiğim Dropdown Menü ye uyarlama şansımız varmı hocam, yardım edebilirsen çok iyi olur