Checkbox dalam codeigniter

saya coba ambil data dari 2 checkbox pria & wanita tapi hanya satu saja yang bisa di ambil, saya coba tambahkan jk[] tetapi ada error yang muncul

model Form_m.php

<?php
defined('BASEPATH') or exit('No direct script access allowed');
class Form_m extends CI_Model
{

    public function get($id = null)
    {
        $this->db->from('form');
        if($id != null){
            $this->db->where('pap_id', $id);
        }
        $query = $this->db->get();
        return $query;

    }

    public function del($id)
    {
        $this->db->where('pap_id',$id);
        $this->db->delete('form');
    }

    public function add($post)
    {
        $params = [
            'nama' => $post ['name'],
            'jenis_kelamin' => $post['jk']
        ];
        $this->db->insert('form', $params);
    }

}

controler Form.php

<?php
defined('BASEPATH') or exit('No direct script access allowed');

class Form extends CI_Controller
{
    function __construct(){
        parent::__construct();
        check_not_login();
        $this->load->model('form_m');
    }
	public function index()
	{
        $data['row'] = $this->form_m->get();
		$this->template->load('template', 'form/form_data',$data);
    }


    public function add(){
        $form = new stdClass();
        $form->pap_id = null;
        $form->nama = null;
        $form->jenis_kelamin = null;
        $data = array(
            'page' => 'add',
            'row' => $form
        );

        $this->template->load('template', 'form/form_multi',$data );
    }

    public function process(){
        $post = $this->input->post(null, TRUE);
        if(isset($_POST['add'])){
            $this->form_m->add($post);
        }

        if($this->db->affected_rows() > 0) {
            echo "<script>alert('Data Berhasil di simpan');</script>";
        }
        echo "<script>window.location='".site_url('form')."';</script>";
    }

    public function del($id)
    {
        $this->form_m->del($id);

        if($this->db->affected_rows() > 0) {
            echo "<script>alert('Data Berhasil di hapus');</script>";
        }
        echo "<script>window.location='".site_url('form')."';</script>";
    }
}

view untuk tampil form_data.php

<section class="content-header">
    <h1>
        Form_data
        <small>Test</small>
    </h1>
    <ol class="breadcrumb">
        <li><a href="#"><i class="fa fa-dashboard"></i></a></li>
        <li class="active">Data Pap</li>
</section>

<!-- Main content -->
<section class="content">

    <div class="box">
        <div class="box-header">
            <h3 class="box-title">Data PAP</h3>
            <div class="pull-right">
                <a href="<?= site_url('form/add') ?>" class="btn btn-primary btn-flat">
                    <i class="fa fa-user-plus"></i> Create
                </a>

            </div>
        </div>
        <div class="box-body table-responsive">
            <table class="table table-bordered table-striped">
                <thead>
                    <tr>
                        <th>#</th>
                        <th>Nama</th>
                        <th>Jenis Kelamin</th>
                        <th>Actions</th>
                    </tr>
                </thead>
                <tbody>
                    <?php $no = 1;
                    foreach ($row->result() as $key => $data) { ?>
                        <tr>
                            <td> <?= $no++ ?>.</td>
                            <td><?= $data->nama ?></td>
                            <td><?= $data->jenis_kelamin ?></td>
                            <td class="text-center" width="160px">
                                <a href="<?= site_url('form/del/'.$data->pap_id) ?>" onclick="return confirm('Apakah anda yakin hapus data?')" class="btn btn-danger btn-xs">
                                    <i class="fa fa-trash"></i> Delete
                                </a>
                            </td>
                        </tr>
                    <?php } ?>
                </tbody>
            </table>
        </div>
    </div>

</section>

form untuk tambah data form_multi.php

<section class="content-header">
    <h1>
        Form Page PAP
        <small>Tester</small>
    </h1>
    <ol class="breadcrumb">
        <li><a href="#"><i class="fa fa-dashboard"></i></a></li>
        <li class="active">PAP</li>
</section>

<!-- Main content -->
<section class="content">

    <div class="box">
        <div class="box-header">
            <h3 class="box-title">Form new </h3>
            <div class="pull-right">
                <a href="<?= site_url('form') ?>" class="btn btn-warning btn-flat">
                    <i class="fa fa-undo"></i> Back
                </a>

            </div>
        </div>
        <div class="box-body">
            <div class="row">
                <div class="col-md-4 col-md-offset-4">
                    <form action="<?=site_url('form/process')?>" method="post">
                        <div class="form-group" width="10px">
                            <label> Nama*</label>
                            <input type="text" name="name" value="<?=$row->nama?>" class="form-control" required>
                        </div>
                        <div class="form-group">
                            <label> Jenis kelamin*</label><br>
                            <input type="checkbox" name="jk" value="pria" <?=$row->jenis_kelamin?>><i>Pria</i>
                            <input type="checkbox" name="jk" value="wanita"<?=$row->jenis_kelamin?>><i>Wanita</i>
                        </div>
                        <div class="form-group">
                            <button type="submit" name="<?=$page?>" class="btn btn-success btn-flat">
                            <i class="fa fa-paper-plane"></i> Save
                            </button>
                            <button type="Reset" class="btn btn-warning btn-flat">Reset</button>
                        </div>
                    </form>
                </div>
            </div>

        </div>
    </div>

</section>

nama database form ada tabel 'pap_id','nama','jenis_kelamin'