Hàm chuyển từ ngày dương lịch sang âm lịch (PHP)

<?php
function INT($d) {
    return floor($d);
}

function jdFromDate($dd, $mm, $yy) {
    $a = INT((14 - $mm) / 12);
    $y = $yy + 4800 - $a;
    $m = $mm + 12 * $a - 3;
    $jd = $dd + INT((153 * $m + 2) / 5) + 365 * $y + INT($y / 4) - INT($y / 100) + INT($y / 400) - 32045;
    if ($jd < 2299161) {
        $jd = $dd + INT((153* $m + 2)/5) + 365 * $y + INT($y / 4) - 32083;
    }
    return $jd;
}

function jdToDate($jd) {
    if ($jd > 2299160) { // After 5/10/1582, Gregorian calendar
        $a = $jd + 32044;
        $b = INT((4*$a+3)/146097);
        $c = $a - INT(($b*146097)/4);
    } else {
        $b = 0;
        $c = $jd + 32082;
    }
    $d = INT((4*$c+3)/1461);
    $e = $c - INT((1461*$d)/4);
    $m = INT((5*$e+2)/153);
    $day = $e - INT((153*$m+2)/5) + 1;
    $month = $m + 3 - 12*INT($m/10);
    $year = $b*100 + $d - 4800 + INT($m/10);
    //echo "day = $day, month = $month, year = $year\n";
    return array($day, $month, $year);
}

function getNewMoonDay($k, $timeZone) {
    $T = $k/1236.85; // Time in Julian centuries from 1900 January 0.5
    $T2 = $T * $T;
    $T3 = $T2 * $T;
    $dr = M_PI/180;
    $Jd1 = 2415020.75933 + 29.53058868*$k + 0.0001178*$T2 - 0.000000155*$T3;
    $Jd1 = $Jd1 + 0.00033*sin((166.56 + 132.87*$T - 0.009173*$T2)*$dr); // Mean new moon
    $M = 359.2242 + 29.10535608*$k - 0.0000333*$T2 - 0.00000347*$T3; // Sun's mean anomaly
    $Mpr = 306.0253 + 385.81691806*$k + 0.0107306*$T2 + 0.00001236*$T3; // Moon's mean anomaly
    $F = 21.2964 + 390.67050646*$k - 0.0016528*$T2 - 0.00000239*$T3; // Moon's argument of latitude
    $C1=(0.1734 - 0.000393*$T)*sin($M*$dr) + 0.0021*sin(2*$dr*$M);
    $C1 = $C1 - 0.4068*sin($Mpr*$dr) + 0.0161*sin($dr*2*$Mpr);
    $C1 = $C1 - 0.0004*sin($dr*3*$Mpr);
    $C1 = $C1 + 0.0104*sin($dr*2*$F) - 0.0051*sin($dr*($M+$Mpr));
    $C1 = $C1 - 0.0074*sin($dr*($M-$Mpr)) + 0.0004*sin($dr*(2*$F+$M));
    $C1 = $C1 - 0.0004*sin($dr*(2*$F-$M)) - 0.0006*sin($dr*(2*$F+$Mpr));
    $C1 = $C1 + 0.0010*sin($dr*(2*$F-$Mpr)) + 0.0005*sin($dr*(2*$Mpr+$M));
    if ($T < -11) {
        $deltat= 0.001 + 0.000839*$T + 0.0002261*$T2 - 0.00000845*$T3 - 0.000000081*$T*$T3;
    } else {
        $deltat= -0.000278 + 0.000265*$T + 0.000262*$T2;
    };
    $JdNew = $Jd1 + $C1 - $deltat;
    //echo "JdNew = $JdNew\n";
    return INT($JdNew + 0.5 + $timeZone/24);
}

function getSunLongitude($jdn, $timeZone) {
    $T = ($jdn - 2451545.5 - $timeZone/24) / 36525; // Time in Julian centuries from 2000-01-01 12:00:00 GMT
    $T2 = $T * $T;
    $dr = M_PI/180; // degree to radian
    $M = 357.52910 + 35999.05030*$T - 0.0001559*$T2 - 0.00000048*$T*$T2; // mean anomaly, degree
    $L0 = 280.46645 + 36000.76983*$T + 0.0003032*$T2; // mean longitude, degree
    $DL = (1.914600 - 0.004817*$T - 0.000014*$T2)*sin($dr*$M);
    $DL = $DL + (0.019993 - 0.000101*$T)*sin($dr*2*$M) + 0.000290*sin($dr*3*$M);
    $L = $L0 + $DL; // true longitude, degree
    //echo "\ndr = $dr, M = $M, T = $T, DL = $DL, L = $L, L0 = $L0\n";
    $L = $L*$dr;
    $L = $L - M_PI*2*(INT($L/(M_PI*2))); // Normalize to (0, 2*PI)
    return INT($L/M_PI*6);
}

function getLunarMonth11($yy, $timeZone) {
    $off = jdFromDate(31, 12, $yy) - 2415021;
    $k = INT($off / 29.530588853);
    $nm = getNewMoonDay($k, $timeZone);
    $sunLong = getSunLongitude($nm, $timeZone); // sun longitude at local midnight
    if ($sunLong >= 9) {
        $nm = getNewMoonDay($k-1, $timeZone);
    }
    return $nm;
}

function getLeapMonthOffset($a11, $timeZone) {
    $k = INT(($a11 - 2415021.076998695) / 29.530588853 + 0.5);
    $last = 0;
    $i = 1; // We start with the month following lunar month 11
    $arc = getSunLongitude(getNewMoonDay($k + $i, $timeZone), $timeZone);
    do {
        $last = $arc;
        $i = $i + 1;
        $arc = getSunLongitude(getNewMoonDay($k + $i, $timeZone), $timeZone);
    } while ($arc != $last && $i < 14);
    return $i - 1;
}

/* Comvert solar date dd/mm/yyyy to the corresponding lunar date */
function convertSolar2Lunar($dd, $mm, $yy, $timeZone) {
    $dayNumber = jdFromDate($dd, $mm, $yy);
    $k = INT(($dayNumber - 2415021.076998695) / 29.530588853);
    $monthStart = getNewMoonDay($k+1, $timeZone);
    if ($monthStart > $dayNumber) {
        $monthStart = getNewMoonDay($k, $timeZone);
    }
    $a11 = getLunarMonth11($yy, $timeZone);
    $b11 = $a11;
    if ($a11 >= $monthStart) {
        $lunarYear = $yy;
        $a11 = getLunarMonth11($yy-1, $timeZone);
    } else {
        $lunarYear = $yy+1;
        $b11 = getLunarMonth11($yy+1, $timeZone);
    }
    $lunarDay = $dayNumber - $monthStart + 1;
    $diff = INT(($monthStart - $a11)/29);
    $lunarLeap = 0;
    $lunarMonth = $diff + 11;
    if ($b11 - $a11 > 365) {
        $leapMonthDiff = getLeapMonthOffset($a11, $timeZone);
        if ($diff >= $leapMonthDiff) {
            $lunarMonth = $diff + 10;
            if ($diff == $leapMonthDiff) {
                $lunarLeap = 1;
            }
        }
    }
    if ($lunarMonth > 12) {
        $lunarMonth = $lunarMonth - 12;
    }
    if ($lunarMonth >= 11 && $diff < 4) {
        $lunarYear -= 1;
    }
    return array($lunarDay, $lunarMonth, $lunarYear, $lunarLeap);
}

/* Convert a lunar date to the corresponding solar date */
function convertLunar2Solar($lunarDay, $lunarMonth, $lunarYear, $lunarLeap, $timeZone) {
    if ($lunarMonth < 11) {
        $a11 = getLunarMonth11($lunarYear-1, $timeZone);
        $b11 = getLunarMonth11($lunarYear, $timeZone);
    } else {
        $a11 = getLunarMonth11($lunarYear, $timeZone);
        $b11 = getLunarMonth11($lunarYear+1, $timeZone);
    }
    $k = INT(0.5 + ($a11 - 2415021.076998695) / 29.530588853);
    $off = $lunarMonth - 11;
    if ($off < 0) {
        $off += 12;
    }
    if ($b11 - $a11 > 365) {
        $leapOff = getLeapMonthOffset($a11, $timeZone);
        $leapMonth = $leapOff - 2;
        if ($leapMonth < 0) {
            $leapMonth += 12;
        }
        if ($lunarLeap != 0 && $lunarMonth != $leapMonth) {
            return array(0, 0, 0);
        } else if ($lunarLeap != 0 || $off >= $leapOff) {
            $off += 1;
        }
    }
    $monthStart = getNewMoonDay($k + $off, $timeZone);
    return jdToDate($monthStart + $lunarDay - 1);
}

function alhn() {
    $arr = array_slice(convertSolar2Lunar(date('d'), date('m'), date('Y'), 7), 0, 3);
    $arr[0] = str_pad($arr[0], 2, '0', STR_PAD_LEFT);
    $arr[1] = str_pad($arr[1], 2, '0', STR_PAD_LEFT);
    return implode("/", $arr);
}

// Âm lịch ngày hôm nay là
echo alhn();
?>