public static function Pfw06($date1, $date2, &$gamb, &$phib, &$psib, &$epsa) {
    $t;

    /* Interval between fundamental date J2000.0 and given date (JC). */
    $t = (($date1 - DJ00) + $date2) / DJC;

    /* P03 bias+precession angles. */
    $gamb = ( -0.052928 +
            ( 10.556378 +
            ( 0.4932044 +
            ( -0.00031238 +
            ( -0.000002788 +
            ( 0.0000000260 ) * $t) * $t) * $t) * $t) * $t) * DAS2R;
    $phib = ( 84381.412819 +
            ( -46.811016 +
            ( 0.0511268 +
            ( 0.00053289 +
            ( -0.000000440 +
            ( -0.0000000176 ) * $t) * $t) * $t) * $t) * $t) * DAS2R;
    $psib = ( -0.041775 +
            ( 5038.481484 +
            ( 1.5584175 +
            ( -0.00018522 +
            ( -0.000026452 +
            ( -0.0000000148 ) * $t) * $t) * $t) * $t) * $t) * DAS2R;
    $epsa = IAU::Obl06($date1, $date2);

    return;
  }