Question

Can anyone point out a good many-to-many database tutorial for CodeIgniter.

Just trying to work out the process of creating, and then updating a many-to-many relationship. My example uses a multi-select of values, wondering how you take care of monitoring changes on update etc.

Answer 1

I’d like to share what I do in my application. This is basically same with my answer in this question.

1. After user submit, and before entering to database, I will fetch the existing data in the database into an array. Example: $collection = array('111', '112', '113', '114'); (This is just for example. In real, it should fetch from database then put the value to array)
2. I will check the new user input in two step. First step is to see if it already in the database or not. If it not, then insert. Otherwise ignore:

   foreach ( $inputs as $input )
   {
     if ( ! in_array($input, $collection) )
     {
       //do insert here
     }
   }

Then in second loop, I do it in reverse, to delete the data that not selected by user.

foreach ( $collection as $data )
{
  if ( ! in_array($data, $inputs) )
  {
    //do delete here
  }
}

In your case, you might or might not need the second loop. I needed this since I make the input as checkboxes, that the user can choose to activate / deactivate, thus I translate it as insert and delete.

Since you will implement it using multi-select, then basically it’s same with my checkboxes.

If you have structure or code example, feel free to share it, and I will help you fine tune it (of course with my style, that might or might not optimized yet).