Dynamic Form PHP and Mysql - Codeinigter

I need to create a form to create assessments, with lots of variable questions. For this I created a form that adds questions, as requested;

The problem is to save on%% of this variety of issues. To be clearer, follow the Code;

<div class="box">
<div class="box-header">




    <ul class="nav nav-tabs nav-tabs-left">
        <li class="active">
            <a href="#add" data-toggle="tab"><i class="icon-plus"></i> 
                <?php echo ('adicionar avaliação');?>
            </a>
         </li>
    </ul>
</div> 


<div class="box-content padded">
<?php echo form_open('admin/avalia/create' , array('class' => 'form-horizontal validatable','target'=>'_top'));?>
    <div class="tab-content">
        <div class="action-nav-normal">
                    <div class=" action-nav-button" style="width:300px;">
                      <a href="#" title="Users">
                        <img src="<?php echo base_url();?>template/images/icons/exam.png" />
                        <span>Total de <?php echo count($avalias);?> Avaliações</span>
                      </a>
                    </div>
                </div>



        <div class="tab-pane  active" id="add">

       <form action="" method="post">  
            <div class="form-actions">           
            <label style="display: block">
             <input class="btn btn-gray" type="button" name="add" value="Adicionar Pergergunta" />
             <button type="submit" class="btn btn-gray"><?php echo ('Salvar Avaliação');?></button>
            </label> 

            </div>
            </br>
            <div class="control-group">
                            <label><?php echo ('Avaliação:');?>
                            <input type="text" class="" name="titulo"/>
                            </label>
                        </div> 
            <label style="display: block">Pergunta: <input type="text" name="pergunta"></label>  
                <fieldset id="inputs_adicionais" style="border: Pergunta" name="pergunta2">  
                </fieldset>  
       </form> 

                    </div>
        </div>        
     </div>
</div>

<-- GERANDO FORMULÁRIOS ADICIONAIS -->
<script type="text/javascript">  
$(document).ready(function(){  

    var input = '<label style="display: block">Pergunta: <input type="text" name="pergunta" /> <a href="#" class="remove">X</a></label>';  
    $("input[name='add']").click(function( e ){  
        $('#inputs_adicionais').append( input );  
    });  

    $('#inputs_adicionais').delegate('a','click',function( e ){  
        e.preventDefault();  
        $( this ).parent('label').remove();  
    });  

});  
</script>  
Segue o código do controller:

function avalia($param1 = '', $param2 = '')
    {
        if ($this->session->userdata('admin_login') != 1)
            redirect(base_url(), 'refresh');
        if ($param1 == 'create') {
            $data['avalia_id']    = $this->input->post('avalia_id');
            $data['titulo']    = $this->input->post('titulo');
            $data['pergunta'] = $this->input->post('pergunta');
            $this->db->insert('avalia', $data);
            redirect(base_url() . 'index.php?admin/avalia/', 'refresh');
        }
        if ($param1 == 'edit' && $param2 == 'do_update') {
            $data['avalia_id']    = $this->input->post('avalia_id');
            $data['titulo']    = $this->input->post('titulo');
            $data['pergunta'] = $this->input->post('pergunta');

            $this->db->where('avalia_id', $param3);
            $this->db->update('avalia', $data);
            redirect(base_url() . 'index.php?admin/avalia/', 'refresh');
        } else if ($param1 == 'edit') {
            $page_data['edit_data'] = $this->db->get_where('avalia', array(
                'avalia_id' => $param2
            ))->result_array();
        }
        if ($param1 == 'delete') {
            $this->db->where('avalia_id', $param2);
            $this->db->delete('avalia');
            redirect(base_url() . 'index.php?admin/avalia/', 'refresh');
        }
        $page_data['avalia']      = $this->db->get('avalia')->result_array();
        $page_data['page_name']  = 'avalia';
        $page_data['page_title'] = ('Avaliação');
        $this->load->view('index', $page_data);
    }

I would like to know how to save the additional fields generated in banco de dados .