PHP Sorting

Question

I am trying to sort an associative array which has multiple vales per entry.

For example

[0] => stdClass Object ( [type] => node [sid] => 158 [score] => 0.059600525242489 )
[1] => stdClass Object ( [type] => node [sid] => 247 [score] => 0.059600525242489 )

I want the array sorted by 'score' (highest score is first index)

How would I do this?

Answer 1

Use the usort function with this comparison function:

function cmpByScore($a, $b) {
    if ($a['score'] == $b['score']) {
        return 0;
    }
    return $a['score'] > $b['score'] ? 1 : -1;
}

usort($array, 'cmpByScore');

Answer 2

You can do this with the usort function. Here's a quick example of how you could do it.

function sortByScore($a, $b) {
  return $a['score'] - $b['score'];  //if a > b it will return positive, a < b will return negative, a == b returns 0
}

usort($array, "sortByScore");

Answer 3

If you have PHP 5.3, you can use closures to make this a little more dynamic and pretty in a simple way:

function sortby(&$array, $key)
{
  usort($array, function($a, $b) {
    return ($a[$key] - $b[$key]);
  });
}

Also note that using the minus in the sort function, as suggested by both tj111 and me, will horribly break if you're also planning to sort strings. In that case, Gumbo's approach is the fail-safe way.

Answer 4

Sample code pasted here. Check this URL: link text

$data[] = array('volume' => 67, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 1);
$data[] = array('volume' => 85, 'edition' => 6);
$data[] = array('volume' => 98, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 6);
$data[] = array('volume' => 67, 'edition' => 7);

In this example, we will order by volume descending, edition ascending.

We have an array of rows, but array_multisort() requires an array of columns, so we use the below code to obtain the columns, then perform the sorting.

// Obtain a list of columns
foreach ($data as $key => $row) {
    $volume[$key]  = $row['volume'];
    $edition[$key] = $row['edition'];
}

// Sort the data with volume descending, edition ascending
// Add $data as the last parameter, to sort by the common key
array_multisort($volume, SORT_DESC, $edition, SORT_ASC, $data);

The dataset is now sorted, and will look like this:

volume | edition
-------+--------
    98 |       2
    86 |       1
    86 |       6
    85 |       6
    67 |       2
    67 |       7