Fixing update teachers.

main/inc/lib/course.lib.php

@@ -4011,6 +4011,8 @@ class CourseManager {
 
         $course_user_table  = Database::get_main_table(TABLE_MAIN_COURSE_USER);
 
+        $alreadyAddedTeachers = CourseManager::get_teacher_list_from_course_code($course_code);
+
         if ($deleteTeachersNotInList) {
 
             // Delete only teacher relations that doesn't match the selected teachers
@@ -4050,24 +4052,24 @@ class CourseManager {
         if ($editTeacherInSessions) {
             $sessions = SessionManager::get_session_by_course($course_code);
 
-            $alreadyAddedTeachers = CourseManager::get_teacher_list_from_course_code($course_code);
-
             if (!empty($sessions)) {
                 foreach ($sessions as $session) {
                     // Remove old and add new
                     if ($deleteSessionTeacherNotInList) {
-                        $coachList = SessionManager::get_users_by_session($session['id'], 2);
-                        // Deleting old coaches
-                        if (!empty($coachList)) {
-                            foreach ($coachList as $coach) {
-                                SessionManager::set_coach_to_course_session($coach['user_id'], $session['id'], $course_code, true);
-                            }
-                        }
-
-                        // Adding new coaches
                         foreach ($teachers as $userId) {
                             SessionManager::set_coach_to_course_session($userId, $session['id'], $course_code);
                         }
+
+                        $teachersToDelete = array();
+                        if (!empty($alreadyAddedTeachers)) {
+                            $teachersToDelete = array_diff(array_keys($alreadyAddedTeachers), $teachers);
+                        }
+
+                        if (!empty($teachersToDelete)) {
+                            foreach ($teachersToDelete as $userId) {
+                                SessionManager::set_coach_to_course_session($userId, $session['id'], $course_code, true);
+                            }
+                        }
                     } else {
                         // Add new
                         foreach ($alreadyAddedTeachers as $userId => $userInfo) {