PMA\libraries\navigation\nodes\Node::getIcon PHP Method

    public function getIcon($match)
    {
        if (!$GLOBALS['cfg']['NavigationTreeEnableExpansion']) {
            return '';
        } elseif ($match && !$this->is_group) {
            $this->visible = true;
            return Util::getImage('b_minus.png');
        } else {
            return Util::getImage('b_plus.png', __('Expand/Collapse'));
        }
    }