I have a photos module and a categories module created and I want a user to be able to add a photo via the photos module and select a category to go along with that photo.

I've got most of it working except when I click save on the photos module, i get an error saying "Message: Undefined index: photo_category_id"

Sorry for the long post, but I wasn't sure what you'd need.

Here's my database tables:

CREATE TABLE `photos` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(255) DEFAULT NULL,
`filename` varchar(255) NOT NULL DEFAULT '',
`published` enum('yes','no') DEFAULT 'yes',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=latin1;

CREATE TABLE `photo_categories` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(255) DEFAULT NULL,
`filename` varchar(255) NOT NULL DEFAULT '',
`published` enum('yes','no') DEFAULT 'yes',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

CREATE TABLE `categories_to_photos` (
`category_id` int(11) unsigned NOT NULL,
`photo_id` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`category_id`,`photo_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;


Here's my Photos module:

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

class Photos_model extends Base_module_model {

function __construct()
{
parent::__construct('photos');
}

// method used to list the data in the admin panel
function list_items($limit = NULL, $offset = NULL, $col = 'id', $order = 'asc')
{
// the data to list
//$this->db->select('id, title, filename, published', FALSE);
$data = parent::list_items($limit, $offset, $col, $order);

return $data;
}

// used to return form information to the form builder class to render the create/edit screens in the admin panel
function form_fields($values = array())
{
$related = array('photo_categories' => 'categories_to_photos_model');

$fields = parent::form_fields($values, $related);

// to limit the image folder to just the projects folder for selection
$fields['image']['class'] = 'asset_select images/uploads/photos';

$upload_path = assets_server_path('uploads/photos', 'images');
$fields['filename'] = array('type' => 'file', 'upload_path' => $upload_path, 'overwrite' => TRUE, 'required' => TRUE);


// fix the preview by adding galleryImages in front of the image path since we are saving it in a subfolder
if (!empty($values['filename']))
{
$fields['filename']['before_html'] = '<div class="img_display"><img src="'.img_path('uploads/photos/thumbs/'.$this->thumb_name($values['filename'])).'" style="float: right;"/></div>';
}

// remove that extra image upload field that always appears
unset($fields['image']);

$CI =& get_instance();
$CI->load->model('photo_categories_model');
//$CI->load->model('categories_model');
$CI->load->model('categories_to_photos_model');

//$category_options = $CI->photo_categories_model->options_list('id', 'title', array('published' => 'yes'));
//$fields['category_id'] = array('type' => 'select', 'options' => $category_options);


return $fields;
}

// saves the data in the categories_to_photos table. Basically saves the link between the photos and the categories
function on_after_save($values)
{
$data = (!empty($this->normalized_save_data['photo_categories'])) ? $this->normalized_save_data['photo_categories'] : array();
$this->save_related('categories_to_photos_model', array('photo_id' => $values['id']), array('category_id' => $data));
}


// creates a thumbnail of an image that is uploaded
function on_after_post($values)
{
$CI =& get_instance();
$CI->load->library('image_lib');

// create the thumbnail if an image is uploaded
if (!empty($CI->upload))
{
$data = $CI->upload->data();
if (!empty($data['full_path']))
{
$thumb_img = assets_server_path('uploads/photos/thumbs/'.$this->thumb_name($data['file_name']), 'images');

// resize to proper dimensions
$config = array();
$config['source_image'] = $data['full_path'];
$config['create_thumb'] = FALSE;
//$config['new_image'] = $thumb_img;
$config['width'] = 1024;
$config['height'] = 768;
$config['master_dim'] = 'auto';
$config['maintain_ratio'] = FALSE;
$CI->image_lib->clear();
$CI->image_lib->initialize($config);
if (!$CI->image_lib->resize())
{
$this->add_error($CI->image_lib->display_errors());
}

// create thumb
$config = array();
$config['source_image'] = $data['full_path'];
$config['create_thumb'] = FALSE;
$config['new_image'] = $thumb_img;
$config['width'] = 185;
$config['height'] = 120;
$config['master_dim'] = 'auto';
$config['maintain_ratio'] = TRUE;
$CI->image_lib->clear();
$CI->image_lib->initialize($config);
if (!$CI->image_lib->resize())
{
$this->add_error($CI->image_lib->display_errors());
}
}
}

return $values;
}


// actually delete the images from the folder when a user delete's them
function on_before_delete($where)
{
$id = $this->_determine_key_field_value($where);
$data = $this->find_by_key($id);
$files[] = assets_server_path('uploads/photos/'.$data->filename, 'images'); // finds the actual image
$files[] = assets_server_path('uploads/photos/thumbs/'.$this->thumb_name($data->filename), 'images'); // finds the thumbnail
foreach($files as $file)
{
if (file_exists($file))
{
@unlink($file);
}
}
}

// gets the thumbnail image name
function thumb_name($image)
{
return preg_replace('#(.+)(\.jpg|\.png)#U', '$1_thumb$2', $image);
}
}

class Photo_model extends Base_module_record {
/*public function get_gallery_image()
{
return '<img src="'.img_path($this->path).'" />';
}*/
function get_image_path()
{
return img_path('uploads/photos/'.$this->filename, NULL, TRUE);
}
function get_thumb()
{
$thumb = $this->_parent_model->thumb_name($this->filename);
return img_path('uploads/photos/thumbs/'.$thumb);
}
}