PHP - sort nth-level subarray

Question

Let's suppose I've a nested PHP array $aaa where the entry $aaa[$bbb][$ccc] is like

array(0 => array('x' => 3, 'y' => 2), 1 => array('x' => 2, 'y' => 1), 2 => array('x' => 4, 'y' => 1))

and let's say I want to order just this array by x value in order to get the array

array(0 => array('x' => 2, 'y' => 1), 1 => array('x' => 3, 'y' => 2), 2 => array('x' => 4, 'y' => 1))

and not modify all the other subarrays. How can I do it? I'm not able to do it with usort and a custom function.

Answer 1

Yet it can be done with usort

$arr = array(
    0 => array('x' => 3, 'y' => 2),
    1 => array('x' => 2, 'y' => 1),
    2 => array('x' => 4, 'y' => 1)
);

function cmp($a, $b)
{
    if ($a['x'] == $b['x']) {
        return 0;
    }
    return ($a['x'] < $b['x']) ? -1 : 1;
}

usort($arr, "cmp");

var_dump($arr);

Result

array(3) {
  [0]=>
  array(2) {
    ["x"]=>
    int(2)
    ["y"]=>
    int(1)
  }
  [1]=>
  array(2) {
    ["x"]=>
    int(3)
    ["y"]=>
    int(2)
  }
  [2]=>
  array(2) {
    ["x"]=>
    int(4)
    ["y"]=>
    int(1)
  }
}