Choosen

<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.min.css" rel="stylesheet" />

<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js"></script>

 jQuery(document).ready(function() {
            $(".select2").select2({
                width: '100%',
                theme: "classic"
            });
        });



'class' => 'select2'