Question

I am trying to calculate percentiles for users in a database. In order to do this I have a $data array that I need to sort.

I have a query object that contains User_ID, Total_User_Orders, and Total_Orders. Here’s how the code looks so far:

// Loop through the users
foreach($query->result() as $row)
{
    (string)$user_id = (string)$row->user_id;

    $data[$user_id] = number_format((($row->total_user_orders/$row->total_orders)*100), 5);
}

// Sort the $data array
array_multisort($data);

print_r($data);

What (I believe) that should do is typecast $row->user_id (an int) as a string. Then, the $data[$user_id] index should be set as a string – right…?

When I sort the array using array_multisort it sorts it as though the index was an Integer, rather than a String. This means it loses the index.

The PHP manual for array_multisort() states, “Associative (string) keys will be maintained, but numeric keys will be re-indexed.”. I have also tried using array_multisort($data, SORT_STRING), but the same output occurs. However – it does work when I do $data['#'.$user_id], but this doesn’t quite feel like the right solution to me!

Can anyone help? Thanks in advance!

Answer 1

I think you’re overcomplicating things. With no testing, I’d think indexing the $data-array like this would work:

$data[(string)$row->user_id] = ...

or

$data[''.$user_id] = ...

EDIT:
Otherwise you could build your array multi-dimensional and sort by one of the indices, like this:

foreach($query->result() as $row) {
  $data[] = array(
    'user_id' => $row->user_id,
    'percent' => number_format((($row->total_user_orders/$row->total_orders)*100), 5);
  );
}

Or you could index by the percentage and sort by the keys (using ksort()):

foreach($query->result() as $row) {
  $data[number_format((($row->total_user_orders/$row->total_orders)*100), 5)] = $row->user_id];
}

The last solution could be dangerous if several users have the same percentage.

Personally I would probably go with the asort() solution mentioned above.