<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.6-rc.0/css/select2.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.6-rc.0/js/select2.min.js"></script>
<script>
$(document).ready(function(){
$('.select2').select2();
});
</script>
<select class="form-control select2" required id="mobile_no" name="mobile_no" style="width:400px;" >
