function askth($tusername, $sid)
{
    $client = new Zend_Http_Client('[STUDENT_LIST_URL]?anony=' . $tusername);
    try {
        $response = $client->request();
    } catch (Exception $e) {
        return false;
    }
    $status = $response->getStatus();
    $body = $response->getBody();
    if ($status == 200 || $status == 400 && !empty($body)) {
        $bodyArray = explode("\n", $body);
        $newArray = array();
        while (list($key, $val) = each($bodyArray)) {
            $dataArray = array('no' => '', 'tname' => '', 'cname' => '', 'sid' => '');
            @(list($dataArray['no'], $dataArray['tname'], $dataArray['ban'], $dataArray['sid']) = explode(",", $val));
            $dataArray_sid = trim($dataArray['sid']);
            if (!empty($dataArray['ban']) && $dataArray_sid == $sid) {
                $newArray[trim($dataArray['ban'])] = trim($dataArray['ban']);
            }
        }
        return renderoptions($newArray);
    } else {
        return false;
    }
}
<?php

require_once '../../config.php';
require_once 'lib/eip.php';
require_login();
$category = optional_param('category', '', PARAM_RAW);
$assign_course = optional_param('assign_course', 0, PARAM_INT);
$capabilitycourse = get_user_capability_course('moodle/role:assign');
$categorycourses = get_courses_wmanagers($category);
$capabilitycategorycourse = array();
foreach ($capabilitycourse as $cc) {
    //$capabilitycategorycourse[] = $categorycourses[$cc->id];
    if ($cc->id != SITEID) {
        if (array_key_exists($cc->id, $categorycourses)) {
            $std = $categorycourses[$cc->id];
            $capabilitycategorycourse[$cc->id] = $std->fullname;
        }
    }
}
if ($assign_course) {
    $context = get_context_instance(CONTEXT_COURSE, $assign_course);
    $assignableroles = get_assignable_roles($context, ROLENAME_BOTH);
    echo renderoptions($assignableroles);
} else {
    echo renderoptions($capabilitycategorycourse);
}