Custom form field not working on server

Question

I created a custom component and in the form one custom field categoryList to list all categories dynamically. Following is the code:

1. formname.xml

   <fieldset addfieldpath="/administrator/components/com_componentname/models/fields">
    <field name="id" type="text" readonly="true" class="readonly" default="0" description="JGLOBAL_FIELD_ID_DESC"/>
   
    <field name="cat_id_01" type="categoryList" onchange="loadSubcategory(1)" label="Category 1" description="Category">
       <option value="">Please select</option>
    </field>
   </fieldset>
   

2. edit.php

   <?php echo $this->form->renderField('cat_id_01'); ?>
   

3. How it appears on localhost: it displays as select-box with category options. This is how I want it to be displayed. php version: 7.0.0

4. models/fields/categoryList.php

       JFormHelper::loadFieldClass('list');
   
               /**
                * Supports an HTML select list of categories
                *
                * @since  1.6
                */
               class JFormFieldCategoryList extends JFormFieldList
               {
                   /**
                    * The form field type.
                    *
                    * @var        string
                    * @since    1.6
                    */
                   protected $type = 'categoryList';
   
                   /**
                    * Method to get the field input markup.
                    *
                    * @return    string    The field input markup.
                    *
                    * @since    1.6
                    */
                   public function getOptions()
                   {
                       $categories[NULL] = 'Please Select';
                       $jinput = JFactory::getApplication()->input;
                       $db = JFactory::getDbo();
                       $query = 'SELECT id, title FROM `#__categories` WHERE parent_id IN (SELECT id from `#__categories` where title="'.$jinput->get('section').'")';
                       $rows = $db->setQuery($query)->loadObjectlist();
                       foreach ($rows as $row) {
                           $categories[$row->id] = $row->title;
                       }
   
                       return $categories;
                   }
   
               }
   

5. How it appears on server: it displays as textbox and somehow the custom field is not working on server. php version: 7.0.17

   <div class="controls">
   <input type="text" name="jform[cat_id_01]" id="jform_cat_id_01" value="110" list="jform_cat_id_01_datalist" onchange="loadSubcategory(1)"><datalist id="jform_cat_id_01_datalist"></datalist>
   </div>
   

6. Joomla version: 3.6.5

I want to display the field as selectbox on server as well.

Answer 1

[This page appears abandoned, so I'll transfer the commented solution as an answer.]

As described in the comments, the issue was with the camelcasing in the filename. For Joomla to access the file, the filename must be in lowercase:

models/fields/categoryList.php should be models/fields/categorylist.php

---

Additionally, I'll offer a revised getOptions() function declaration with Joomla query building syntax to replace the raw sql string and do my best to implement Joomla's php coding standards.

public function getOptions()
{
    $section = JFactory::getApplication()->input->get->get("section");
    $db = JFactory::getDbo();

    $subquery = $db->getQuery(true)
        ->select($db->quoteName("id"))
        ->from($db->quoteName("#__categories"))
        ->where($db->quoteName("title") . " = " . $db->quote($section));

    $query = $db->getQuery(true)
        ->select($db->quoteName(["id", "title"]))
        ->from($db->quoteName("#__categories"))
        ->where($db->quoteName("parent_id") . " IN (" . $subquery . ")");

    $rows = $db->setQuery($query)->loadObjectlist();
    $categories[null] = 'Please Select';
    foreach ($rows as $row)
    {
        $categories[$row->id] = $row->title;
    }
    return $categories;
}