对具有多个值的数组进行排序比较

Question

I have the following array

$postarray[] = array( 'total'   => '6.5', 'points'  => '300' );
$postarray[] = array( 'total'   => '11.4', 'points' => '320' );
$postarray[] = array( 'total'   => '6.5', 'points'  => '340' );
$postarray[] = array( 'total'   => '2.6', 'points'  => '300' );
$postarray[] = array( 'total'   => '12.8', 'points' => '320' );

And I want to sort it into the following. Notice that if the points are equal then it compares total and sorts it in ascending order.

$postarray[] = array( 'total'   => '6.5', 'points'  => '340' );
$postarray[] = array( 'total'   => '12.8', 'points' => '320' );
$postarray[] = array( 'total'   => '11.4', 'points' => '320' );
$postarray[] = array( 'total'   => '6.5', 'points'  => '300' );
$postarray[] = array( 'total'   => '2.6', 'points'  => '300' );

So far I have used usort to sort according to the points but I'm not sure how to sort the total field too.

    function sortByOrder($a, $b) {
        if ($b['points'] > $a['points']) {
            return $b['points'] - $a['points'];
        } elseif ($b['points'] == $a['points']) {
            return 0;
        }
    }
    usort($postarray, 'sortByOrder');

Answer 1

array_multisort() with array_column() as of PHP 5.5.0:

array_multisort(array_column($postarray, 'points'), SORT_DESC,
                array_column($postarray, 'total'),  SORT_DESC,
                $postarray);