Ajax response render to datatables column

Well, that was a tough one huh? :)

Anyway, after a lot of struggle, I decided to make a different approach to the problem:

1. I changed the initialization script to it's "default" state:

   oTable = $('#companies').dataTable({
   "processing": true,
   "serverSide": true,
   "ajax": {
       "url": "ajax/companies/get_companies.ajax.php"
       "type": "POST"
   },
   "columns": [
       { "bSearchable": true, "data": "company_name" },
       { "bSearchable": true, "data": "company_field" },
       { "bSearchable": true, "data": "company_area" },
       { "bSearchable": true, "data": "relative_items" },
       { "bSearchable": false, "data": "subscription_end" }
   ],
   "order": [[1, 'asc']] });
   

2. I decided that any changes should take place not in the initialization script, but in the ajax file that provided the results to the table ( ajax/companies/get_companies.ajax.php ).
   This script is the default server-side script which I got from datatables.net. Link here: http://www.datatables.net/examples/server_side/simple.html

Initially I would just define the columns array for the datatables like that:

$columns = array(
    array( 'db' => 'name', 'dt' => 'company_name' ),
    array( 'db' => 'business_field',  'dt' => 'company_field' ),
    array( 'db' => 'area',   'dt' => 'company_area' ),
    array( 'db' => 'items',     'dt' => 'relative_items' ),
    array(
        'db'        => 'subscription_ends',
        'dt'        => 'subscription_end',
        'formatter' => function( $d, $row ) {
            return date( 'd M Y', strtotime($d));
        }
    )
);

The WORKING SOLUTION was to use the 'formatter' also for the fourth column (as I was already doing for the fifth column). Like that:

$columns = array(
array( 'db' => 'name', 'dt' => 'company_name' ),
array( 'db' => 'business_field',  'dt' => 'company_field' ),
array( 'db' => 'area',   'dt' => 'company_area' ),
array( 
    'db'        => 'items',     
    'dt'        => 'relative_items',
    'formatter' => function( $d, $row ) {

        $conn = ... //CONNECTION TO THE DATABASE

        $items_array = str_replace("|", ", ", substr(substr($d, 1), 0, -1));
        //format the items strin from this: |3|12|7| to comma-separated 3,12,7

        $arr = explode(", ", $items_array);
        //create my array

        $first = reset($arr);
        $last = end($arr);

        foreach ($arr as $item_id) { //For each Id, get the corresponding Item Name:
            $get_item_name = mysql_query("SELECT name FROM ".DB_TABLE_PREFIX."items WHERE id = '$item_id' ");
            $row = mysql_fetch_array($get_item_name);
            //Append to the results comma and space (", ") except to the last one...
            if ($item_idx == $last) {
                $res .= $row["name"];
            }else{
                $res .= $row["name"];
                $res .= ", ";
            }
        }
        return $res;
        //and voila! worked like charm!
        //column now shows: Jacket, Shirt, T-shirt (instead of id's: 3, 12, 7)
    }
),
array(
    'db'        => 'subscription_ends',
    'dt'        => 'subscription_end',
    'formatter' => function( $d, $row ) {
        return date( 'd M Y', strtotime($d));
        }
    )
);

So, the solution was simply to look at the problem from a different angle!

Hope this helps some people!