private static function renameKeys($arr, $xlat)
{
if (empty($xlat)) {
return $arr;
}
$res = [];
$occupied = array_flip($xlat);
foreach ($arr as $k => $v) {
if (isset($xlat[$k])) {
$res[$xlat[$k]] = $v;
} elseif (!isset($occupied[$k])) {
$res[$k] = $v;
}
}
return $res;
}