Add comment about Suhosin limits blocking courses import - refs BT#10760

main/coursecopy/import_backup.php

@@ -62,6 +62,10 @@ if (Security::check_token('post') && (
     $error = false;
     if (isset($_POST['action']) && $_POST['action'] == 'course_select_form') {
         // Partial backup here we recover the documents posted
+        // This gets $_POST['course']. Beware that when using Suhosin,
+        // the post.max_value_length limit might get in the way of the
+        // restoration of a course with many items. A value of 1,000,000 bytes
+        // might be too short.
         $course = CourseSelectForm::get_posted_course();
 
     } else {