public static function Cpv(array $pv, array &$c) {
    // Added in PHP porting... initialize $c array
    $c[] = [0, 0, 0];
    $c[] = [0, 0, 0];

    IAU::Cp($pv[0], $c[0]);
    IAU::Cp($pv[1], $c[1]);

    return;
  }