how to only show its group user?

function user_list()
{
    global $phpc_script, $phpcdb;

   $list = tag('ul');
    $tbody = tag('ul');

    $tbody->add(tag('span', attrs('class="phpc-dropdown-list"'),
        tag('span', attrs('class="phpc-dropdown-list-header"'),
            tag('span', attrs('class="phpc-dropdown-list-title"'))),__("Username")),$list);

    foreach($phpcdb->get_users() as $user) {
    $group_list = array();

    foreach($user->get_groups() as $group) {
        $group_list[] = $group['name'];
    }
    $groups = implode(', ', $group_list);

    $tbody->add(tag('li', tag('a', attrs("href='$phpc_home_url?action=display_week&week=2&year=2015&uid={$user->uid}'"),$user->username)

                ));

} 

    return 
        tag('span',$tbody); 

}

in it , i want to show one's group user , for example ; group A have a,b,c,d for people, group B have e,f,g,h,i, so that i want to show group A will just dispaly a b c d people . how to do it?

i use it in display_week.php can display i want . https://github.com/sproctor/php-calendar/issues/126

sproctor / php-calendar

how to only show its group user? #129