echo '
                            <select multiple id="feature_'.$tab_features['id_feature'].'_value" name="feature_'.$tab_features['id_feature'].'_value[]"
                                onchange="$(\'.custom_'.$tab_features['id_feature'].'_\').val(\'\');">
                                <option value="0">---&nbsp;</option>';

                        foreach ($featureValues AS $value)
                        {
                            if ($current_item == $value['id_feature_value'])
                                $custom = false;
                            echo '<option value="'.$value['id_feature_value'].'"'.(($current_item == $value['id_feature_value']) ? ' selected="selected"' : '').'>'.substr($value['value'], 0, 40).(Tools::strlen($value['value']) > 40 ? '...' : '').'&nbsp;</option>';
                        }

                        echo '</select>';

public function addFeaturesToDB($id_feature, $id_value, $cust = 0)
    {
        if ($cust)
        {
            $row = array('id_feature' => (int)($id_feature), 'custom' => 1);
            Db::getInstance()->autoExecute(_DB_PREFIX_.'feature_value', $row, 'INSERT');
            $id_value = Db::getInstance()->Insert_ID();
            $row = array('id_feature' => (int)($id_feature), 'id_product' => (int)($this->id), 'id_feature_value' => (int)($id_value));
            Db::getInstance()->autoExecute(_DB_PREFIX_.'feature_product', $row, 'INSERT');
            return ($id_value);
        }else{            
            $row = array();
                foreach ($id_value AS $val)
                $row[] = '('.(int)($id_feature).', '.(int)($this->id).', '.(int)($val).')';
            return Db::getInstance()->Execute(
            'INSERT INTO `'._DB_PREFIX_.'feature_product` (`id_feature`, `id_product`, `id_feature_value`)
            VALUES '.implode(',', $row));
                
                
                //$row = array('id_feature' => (int)($id_feature), 'id_product' => (int)($this->id), 'id_feature_value' => (int)($id_value));
                
                
                
                
        //Db::getInstance()->autoExecute(_DB_PREFIX_.'feature_product', $row, 'INSERT');
        //if ($id_value)
        //    return ($id_value);
        }
        
    // Db::getInstance()->Execute('
    // INSERT INTO `'._DB_PREFIX_.'feature_product` (`id_feature`, `id_product`, `id_feature_value`)
    // VALUES ('.(int)($id_feature).', '.(int)($this->id).', '.(int)($id_value).')'
    // );
    }