next element in 2 array loop php

Question

First of all, I apologize for my bad English. I have 2 array. First one is Sections and second one Lessons. I'm trying to get $next_lesson id element using this code:

foreach ($sections as $key => $section):
  $lessons = $this->crud_model->get_lessons('section', $section['id'])->result_array();
    foreach ($lessons as $key => $lesson):
       $current_lesson = $lesson['id'];
       $next = $lessons[$key+1];
       $next_lesson = $next['id'];
    endforeach;
endforeach;

Javascript redirect:

  window.location.href = "<?php echo site_url('home/lesson/')."/".$course_id."/".$next_lesson; ?>";

but after 1 lesson loop $next_lesson getting first value of section 1. What should I do to move to the second part when the last lesson of the first part is over?

Database structure screenshot if needed

Answer 1

I'd say it is more about data structure in the database and querying it than a php algorithm (this 2 loops force you to query all the lessons and it might be time consuming).

First of all you'd have to ask yourself : what is the ordering parameter ? (it is not obvious in the screenshot provided).

Let's say it's the order (edited from comment) field, that is unique among all the lessons (not reset for a new section). In such a case, a new sql query would be :

    SELECT * -- or just id 
    FROM lesson
    WHERE `order` > ?
    ORDER BY `order` ASC
    LIMIT 1;

With the parameter (the ? ) equals to the current lesson order field, generally passed with the method of the ORM used to query the Database.