Панель фильтрации сворачивается при применении фильтра - Разработка расширений для Joomla 3.x

  protected function populateState($ordering = null, $direction = null) {
    $this->setState('filter.search', $this->getUserStateFromRequest($this->context . '.filter.search', 'filter_search'));
    $this->setState('filter.category_id', $this->getUserStateFromRequest($this->context . '.filter.category_id', 'filter_category_id'));
    parent::populateState('ordering', 'asc');
  }

  protected function getStoreId($id = '') {
    $id .= ':'.$this->getState('filter.search');
    $id .= ':'.$this->getState('filter.category_id');
    return parent::getStoreId($id);
  }

  <fields name="filter">
    <field name="search" type="text" label="COM_CONTENT_FILTER_SEARCH_DESC" hint="COM_TEACHING_STAFF_SEARCH_FILTER_FIO" />
    <field name="category_id" type="category" label="JOPTION_FILTER_CATEGORY" extension="com_teaching_staff" description="JOPTION_FILTER_CATEGORY_DESC" onchange="this.form.submit();" >
      <option value="">JOPTION_SELECT_CATEGORY</option>
    </field>
  </fields>

  public function __construct($config = array()) {
    if (empty($config['filter_fields']))
      $config['filter_fields'] = array('ordering', 'fio', 'post', 'tscat', 'commonls', 'tsls', 'id');
    parent::__construct($config);
  }

if ( empty( $config['filter_fields'] ) ) {
	$config['filter_fields'] = array(
		'title', 'state', 'ordering', 'created_by', 'created', 'id', 'author_id', 'catid',
	        'category_id',
		'published',
	);
}

$config['filter_fields'] = array('ordering', 'fio', 'post', 'tscat', 'commonls', 'tsls', 'id', 'category_id');

$config['filter_fields'] = array('fio', 'category_id');

$config['filter_fields'] = array(
				'id', 'a.id',
				'title', 'a.title',
				'alias', 'a.alias',
				'checked_out', 'a.checked_out',
				'checked_out_time', 'a.checked_out_time',
				'catid', 'a.catid', 'category_title',
				'state', 'a.state',
				'access', 'a.access', 'access_level',
				'created', 'a.created',
				'created_by', 'a.created_by',
				'created_by_alias', 'a.created_by_alias',
				'ordering', 'a.ordering',
				'featured', 'a.featured',
				'language', 'a.language',
				'hits', 'a.hits',
				'publish_up', 'a.publish_up',
				'publish_down', 'a.publish_down',
				'published', 'a.published',
				'author_id',
				'category_id',
				'level',
				'tag'
			);