Display specific Joomla user groups

Question

This code snippet below shows the list of all Joomla user groups(registered,editor.superuser and ...) at component

    // load in joomla user groups
    $qry = "SELECT * FROM #__usergroups ORDER BY lft";
    $db->setQuery($qry);

    $this->groups = $db->loadObjectList();

    $group_index = array();

    foreach ($this->groups as &$group)
    {
        $group_index[$group->id] = &$group;

        if ($group->parent_id == 0)
        {
            $group->level = 0;  
        } else {
            $group->level = $group_index[$group->parent_id]->level + 1;
        }

        $group->display = str_repeat("- ", $group->level) . $group->title;
    }

    array_unshift($this->groups, JHTML::_('select.option', '', JText::_("JOOMLA_USERGROUP"), 'id', 'display'));
    $this->jgroup_select = JHTML::_('select.genericlist',  $this->groups, 'usergroup', 'class="inputbox" size="1" onchange="document.fssForm.submit( );"', 'id', 'display', $this->usergroup);

now I want to show only registered user and manager user list or only registered user

Answer 1

A basic query to to select parent and its children from a nested table, taken from Joomla\CMS\Table\Nested::getTree():

$query = $db->getQuery(true)
    ->select('n.*')
    ->from('#__usergroups AS n, #__usergroups AS p')
    ->where('n.lft BETWEEN p.lft AND p.rgt')
    ->where('p.id = ' . (int) $groupId)
    ->order('n.lft');

$this->groups = $db->setQuery($query)->loadObjectList();

Where $groupId is the topmost group's ID.

You also need to modify your code here:

if ($group->parent_id == 0)

By adding a check for array element with topmost group's ID :

if (!isset($group_index[$group->parent_id]) || $group->parent_id == 0)

This is because the parent of your topmost group is not retrieved. Alternatively, add a counter to the loop and check for first run:

foreach ($this->groups as $key => &$group)
{
    ...
    if ($key === 0)
    {
        $group->level = 0;
        ...