Использование типов полей для фильтров - Модификации расширений для Joomla

public function getSelect()
{
     return $this->getOptions();
}

$city = new JFormFieldCity();
$this->filter_city = $city->getSelect();

$this->filter_city = JFormFieldCity::getSelect();

<?php
defined('_JEXEC') or die;

jimport('joomla.form.helper');
JFormHelper::loadFieldClass('list');

class JFormFieldCity extends JFormFieldList
{
	protected $type = 'City';
 
	protected function getOptions() 
	{
		$db = JFactory::getDBO();

		$query = $db->getQuery(true);
		$query->select('id, title')
				->from('#__city');
		$db->setQuery($query);
		$cities = $db->loadObjectList();

		$options = array();
		if ($cities)
		{
			foreach($cities as $city) 
			{
				$options[] = JHtml::_('select.option', $city->id, $city->title);
			}
		}
		$options = array_merge(parent::getOptions(), $options);

		return $options;
	}
}

JLoader::discover('JForm', JPATH_COMPONENT_ADMINISTRATOR . '/models/fields');

JLoader::discover('JFormField', JPATH_COMPONENT_ADMINISTRATOR . '/models/fields');

JLoader::discover('JFormField', JPATH_COMPONENT_ADMINISTRATOR . '/models/fields');
$result = JFormFieldHelloWorld::getOptions();

static function getSelect()
{
     return $this->getOptions();
}

$city = new JFormFieldCity();
$this->filter_city = $city->getSelect();

Fatal error: Call to a member function children() on a non-object in /var/www/vhosts/сайт/httpdocs/libraries/joomla/form/fields/list.php on line 89

$options = array_merge(parent::getOptions(), $options);

public function getSelectList()
{
	return JHtml::_('select.genericlist', $this->getOptions(), 'city');
}

JHtml::_('eshtml.filters.имяфильтра')

JHtml::addIncludePath(JPATH_COMPONENT . '/helpers/html');

JLoader::register('SelectReturn', JPATH_COMPONENT_ADMINISTRATOR . '/helpers/html/filters.php');

protected function getOptions() 
{
    $options = SelectReturn::getSelect(false, 'city', array('id','title'));
    $options = array_merge(parent::getOptions(), $options);
                
    return $options;
}

<?php
// No direct access to this file
defined('_JEXEC') or die;

abstract class SelectReturn
{
	public static function getData($table = 'city', $param = array('id', 'title')) 
	{
            $db = JFactory::getDBO();
            $query = $db->getQuery(true);
            $query->select($param[0].','.$param[1])->from('#__'.$table);
            $db->setQuery($query);
            $return = $db->loadAssocList();
            return $return;
	}
	
	public static function getSelect($data = false, $table = 'city', $param = array('id', 'title'))
	{	
	    if(!$data)
            {
                $data = self::getData($table, $param);
            }
            $options = array();
            foreach($data as $item) 
            {
                    $options[] = JHtml::_('select.option', $item[$param[0]], $item[$param[1]]);
            }
            return $options;
	}
}