使用逗号分隔符一列上传多个图像并插入文件名

Question

using for loop i had upload multiple images and image names saved in database in single column using comma separator is working fine but problem is that now i have to edit same form having five images i have to edit one or two images save the form it should save images path previous one as it is and also new edited.....

    $target = "upload/storage_logo/"; 
    $target = $target . basename( $_FILES['add_facility_logo']['name'] ) ; 

if(count($_FILES["add_storage_image"]['name'])>0) {

    for($j=0; $j < count($_FILES["add_storage_image"]['name']); $j++) 
    { 
       $target = "upload/storage_images/"; 
       $target = $target . basename( $_FILES['add_storage_image']['name'][$j] ) ; 

       if( ($_FILES['add_storage_image'] ['error'][$j] == 0) && ($_FILES ['add_storage_image'] ['size'][$j] > 0)) { 

        move_uploaded_file($_FILES['add_storage_image']['tmp_name'][$j], $target);

        }

    }

}