function VerifyFixedSchedule($columns,$columns_var,$update=false)
{
   
    $qr_teachers=  DBGet(DBQuery('select TEACHER_ID,SECONDARY_TEACHER_ID from course_periods where course_period_id=\''.$_REQUEST['course_period_id'].'\''));
    $teacher=($_REQUEST['tables']['course_periods'][$_REQUEST['course_period_id']]['TEACHER_ID']!=''?$_REQUEST['tables']['course_periods'][$_REQUEST['course_period_id']]['TEACHER_ID']:$qr_teachers[1]['TEACHER_ID']);
    $secteacher=($_REQUEST['tables']['course_periods'][$_REQUEST['course_period_id']]['SECONDARY_TEACHER_ID']!=''?$_REQUEST['tables']['course_periods'][$_REQUEST['course_period_id']]['SECONDARY_TEACHER_ID']:$qr_teachers[1]['SECONDARY_TEACHER_ID']);
//    $secteacher=$qr_teachers[1]['SECONDARY_TEACHER_ID'];
    
    if($_REQUEST['tables']['course_periods'][$_REQUEST['course_period_id']]['TEACHER_ID']!='')
     $all_teacher=$teacher.($secteacher!=''?','.$secteacher:'');
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.