如何从codeigniter中选择有关“optgroup”的信息？

Im making an "admin" page to upload photos to different categories, so there is an <input type="file"> and a <select> that contains categories and subcategories organized in optgroups if a category have a subcategory, or just without the optgroup if it is just a category.

<?php echo form_open_multipart('principal/subir_foto');?>  
             <div class='input-group'>                                  
                <label for="img" class='control-label'>Seleccionar:</label>
                <input id="img" required="true" type='file' name='imagen'/>
             </div>
             <div class='input-group'>                                               
                <label for="categoria" class='control-label'>Elegir Categoria:</label>
                <select class='selectpicker form-control' name='cat_op' data-width='auto'>
                    <?php 
                        foreach ($categorias as $row_cat) {                         
                            if($row_cat->tiene_subcat > 0){
                                echo "<optgroup value='".$row_cat->nom_cat ."' label='". $row_cat->nom_cat ."'>";
                                foreach ($subcat as $row_subcat) {
                                    if($row_subcat->id_cat === $row_cat->id_cat){
                                        echo "<option value=". $row_subcat->nom_subcat ."> ". $row_subcat->nom_subcat ."</option>";
                                    }                                       
                                }
                                echo "</optgroup>";
                            }
                            else{
                                echo "<option value='" . $row_cat->nom_cat . "'>". $row_cat->nom_cat . "</option>";
                            }
                        }
                    ?>
                </select>                              
            </div>                
            <div class='input-group'>
                <input type='submit' name='agregar' value="Agregar">
            </div>             
           </form>

So when the code is interpreted by the server, the <select> tag appears like this:

<label class='control-label'>Elegir Categoria:</label>
 <select class='selectpicker form-control' name='cat_op' data-width='auto'>

   <optgroup value='SALAS' label='SALAS'>

     <option value=RAWSON> RAWSON</option>
     <option value=CAPITAL> CAPITAL</option>

   </optgroup>

   <option value='SERVICIOS FUNERARIOS'>SERVICIOS FUNERARIOS</option>
   <option value='ATAUDES'>ATAUDES</option>
   <option value='FLORES'>FLORES</option>                   
</select>

So, when the submit button is pressed, in my Code Igniter controller named "Principal" and in the method "subir_foto" I can get access to $this->input->post('cat_op') thats gives me the option selected when submit, but how can I get the optgroup value also, because I need to have the subcategory and category name. I hope I have expressed my problem well

This is how the selectpicker is displayed

Thanks, is my first question.

Well, I finally made the logic in "Principal" controller so I can know if it is a category or a subcategory and know also from wich category inherits.

public function subir_foto(){
    $opcion = $this->input->post('cat_op');//obtengo el valor de "option" elegido
    $op_row = $this->datos_model->getWhere('sub_categorias',array('nom_subcat'=>$opcion));#busco en la tabla sub_categorias por el nombre. Si lo encuentra, busco en la tabla categoria por id_cat
    if(!empty($op_row)){
        foreach ($op_row as $row) {
            $id_Cat = $row->id_cat;
            $subcat = $row->nom_subcat;
        }           
        $cat_row = $this->datos_model->getWhere('categorias',array('id_cat'=>$id_Cat));
        foreach ($cat_row as $row) {
           $cat = $row->nom_cat;
        }                        
    }
    else{
        $cat = $opcion;
        $subcat = null;
    }

Then I can Inset the photo in the table of my DB like this (Of course I have skipped the validation part in the code)

$datos = $this->upload->data();
        $row = array(
            'ruta'=>$datos['file_path'],
            'nom_img'=>$datos['file_name'],
            'categoria'=>$cat,
            'subcat'=>$subcat,
            'alt'=>$alt,
            'height'=>$datos['image_height'],
            'width'=>$datos['image_width'],'size'=>$datos['file_size']);
        $this->datos_model->insertar('imagenes',$row);
        $data['error'] = 'Archivo '. $datos['file_name'] .' subido exitosamente';

        $this->load->view('templates/header', $data);
        $this->load->view('pages/admin', $data);
        $this->load->view('templates/footer');

This is the Model method "getWhere" when I call it from $this->datos_model->getWhere(table,array);

function getWhere($tabla,$arreglo){
        $query = $this->db->get_where($tabla, $arreglo);
        if($query->num_rows() > 0){
            return $query->result();
        }
        else{
            return null;
        }
    }

So basically when I get the option selected, I first make a query where "name" = option in the "Subcategory" table of mi DB. If the query is not empty it means that the option corresponds to a subcategory. So now I need to know Of which category underlies that subcat.(I have id_cat as a foreign key in "subcategory" table) So I make another query where "id_cat" = id_cat in my "categories" table of the DB. Finally I can get the name of the father category.

I hope I made myself clear. Thanks

The <optgroup> tag does not have a value attribute. It's purely a formatting instruction for the browser.

If you need to distinguish between multiple similar options in a <select> element, include all of the necessary data in the value of the <option> elements. For instance, you might include the category and subcategory names separated by a colon:

echo "<option value='"
    . $row_cat->nom_cat . ":" . $row_subcat->nom_subcat
    . "'>" . $row_subcat->nom_subcat . "</option>";