combobox dinamis

<select name="role" id="role">
    <option value="asdos">Asdos</option>
    <option value="dosen">Dosen</option>
    <option value="laboran">Laboran</option>
    <option value="admin">Admin</option>
</select>
<span id="prak-form"></span>
 
<script type="text/javascript">
$(function(){
    $('#role').change(function(){
        var prak = $('#prak-form');
         if(this.value == 'asdos'){
            $.get('form/get_praktikum', function(data){
                    if(data.length != 0){
                        var i;
                        var text = '<select name="praktikum">';
                        for(i=0; i < data.length; i++){
                            text += '<option value="'+data[i]+'">'+data[i]+'<\/option>';
                        }
                        text += '<\/select>';
                    }else{
                        prak.text('Praktikum Kosong');
                    }
                },
                'json'
            );
         }
    });
});
</script>
 
//Form Controller
function get_praktikum()
{
    //query bla bla bla..
    //cetak berupa javascript array literal,
    //misal
    echo '["Praktikum A", "Praktikum B", "Praktikum C"]';
}