Chaining Spaceship¶

<?php


function foo($a, $b) {
    return $a[0] <=> $b[0] ?:
           $a[1] <=> $b[1] ?:
           $a[2] <=> $b[2] ?:
               0;
}


$array = [
    [1, 2, 3],
    [1, 3, 5],
    [1, 2, 4],
    [0, 2, 3],
    ];

usort($array, foo(...));
print_r($array);

It is possible to chain several spaceship operations by using the coalesce operator ?:. When the first spaceship operator returns 1 or -1, its value is immediately used. On the other hand, when the operation leads to 0, the coalesce ?: uses the else branch, where the second spaceship operator is used, to the same effect.

This expression here replaces a call to array_multi_sort().

And of course, literally chaining spaceships together is a very bad idea.

See Also¶

array_multisort (PHP manual)
chaining spaceships [Try me]

PHP Features¶

Last updated: 14 July 2026