moodle第一次没有在下拉列表中显示值

Question

I am facing a problem. I have to add value to drop down list in moodle. I have created a function which fetch result from database and show in drop down box. When i add new course in moodle then first time drop down list seems empty. when i enter activity in same course again, it show value. But it doesn't show values at first attempt. I am using this function

function getActivities($cid)
 {
        global $DB;
        global $CFG;

    $res=array();
    $sql="SELECT m.id as id, m.name as name
    FROM {$CFG->prefix}course_modules as cm,{$CFG->prefix}modules as m,{$CFG->prefix}course as c,{$CFG->prefix}activitysetmodule as asm
    WHERE asm.course = cm.course
    AND asm.course = c.id
    AND cm.module = m.id
    AND cm.course =$cid";
    $rec2=array();
    $rec1=array();
    $result=$DB->get_records_sql($sql);
    foreach($result as $rec)
    {
        $rec2[]=$rec->name;
    }
    foreach($result as $rec)
    {
        $rec1[]=$rec->id;
    }
$c = array_combine($rec1,$rec2);

return $c;

Please help me to sought it out.

Answer 1

Its because there won't be any modules for the course when it's first created, $cid will be blank.

Also for Moodle 2, you should use the {tablename} syntax rather than {$CFG->prefix}

Also there is a function that retrieves data as a menu for you :

function getActivities($cid) {
    global $DB;

    if (empty($cid)) {
        // New course.
        return array();
    }

    $sql = "SELECT m.id, m.name
            FROM {modules} m
            JOIN {course_modules} cm ON cm.module = m.id AND cm.course = :courseid";

    $result = $DB->get_records_sql_menu($sql, array('courseid' => $cid));

    return $result;
}