usort() has different behavior PHP / KPHP

[comm644]

When compare are equal then behaviour diffrent.

<?php


class Data
{
  public string $key;
  public string $data;

  public function __construct(string $key, string $data)
  {
    $this->key = $key;
    $this->data=$data;
  }
}

/** @var Data[] $data */
$data[] = new Data("keyA", "value1");
$data[] = new Data("keyA", "value2");
$data[] = new Data("keyB", "value3");
$data[] = new Data("keyB", "value4");


usort($data, function (Data $x, Data $y) {
  return strcmp($x->key, $y->key);
});

foreach ($data as $item ){
  echo "{$item->key} {$item->data}\n";
}

//check strcmp()
$rc = strcmp("keyA", "keyA");
echo sprintf("cmp: rc=%d\n", $rc);

out:

keyA value1
keyA value2
keyB value4  <<< changed
keyB value3  <<< changed

expected:
keyA value1
keyA value2
keyB value3
keyB value4