please help, how to edit checkbox on codeigniter

$in my view :

 <?php echo form_checkbox("kpd_yth[]", "Kabid Umum",set_checkbox("kpd_yth[]","Kabid Umum" )); ?>Kabid Umum</br>
    <?php echo form_checkbox("kpd_yth[]", "Kabid Tiga", set_checkbox("kpd_yth[]","Kabid Tiga" )); ?>Kabid Tiga</br>

$and in my controllers

'kpd_yth' => implode(',',$this->input->post('kpd_yth'));