checkbox warna

//Ini form inputnya
 <div class="form-group">
        <label>Warna :</label>
        <?php
        $list_warna=array('Hitam','Merah','Kuning','Hijau');
        foreach($list_warna as $w):
        ?>
        <div class="checkbox">
          <label>
            <input type="checkbox" name="warna[]" value="<?=$w?>">
            <?=$w?>
          </label>
        </div>
        <?php endforeach;?>
        <div class="checkbox">
          <label>
            <input type="checkbox" />
            <input type="text" name="warna[]" />
          </label>
        </div>
</div>

//Ini proses di serversidenya
function create(){
        $data_post = $this->input->post();
        foreach($data_post as $key=>$value){
            if(is_array($value)){
                //ini fungsi implodenya
                $data_to_save[$key] = implode("|",array_filter($value));
            }else{
                $data_to_save[$key] = $value;
            }

        }
    }


//ini form editnya
 <div class="form-group">
        <label>Warna :</label>
        <?php
        $list_warna=array('Hitam','Merah','Kuning','Hijau');
        $array_warna=explode('|',$warna);
        $diff=array_diff($array_warna,$list_warna);
        foreach($list_warna as $w):
        ?>
        <div class="checkbox">
          <label>
            <input type="checkbox" name="warna[]" value="<?=$w?>"<?=in_array($w,$array_warna)?" checked":""?>>
            <?=$w?>
          </label>
        </div>
        <?php endforeach;?>
        <div class="checkbox">
          <label>
            <input type="checkbox" <?=!empty($diff)?' checked':''?>/>
            <input type="text" name="warna[]" <?=!empty($diff)?'value="'.implode('',$diff).'"':''?>/>
          </label>
        </div>
</div>