class-imsakiyah.php

<?php
/**
 * Description of Imsakiyah
 *
 * @author Misbahul D Munir <misbahuldmunir@gmail.com>
 */
class Imsakiyah
{
	// panjang 1 tahun rata-rata dalam detik
	const YEAR_LENGTH = 31557600;

	public $bujur;
	public $lintang;
	public $date;
	public $timestamp;
	public $timeZone;
	public $rawOffset;
	public $ketinggian = 100;

	public function rules()
	{
		return[
			[['bujur', 'lintang'], 'required'],
			[['date'], 'default', 'value' => date('d/m/Y')],
			[['date'], 'date', 'format' => 'dd/MM/yyyy', 'timestampAttribute' => 'timestamp'],
			[['lintang'], 'number', 'min' => -90, 'max' => 90],
			[['bujur'], 'number', 'min' => -180, 'max' => 180],
			[['timeZone'], 'default', 'value' => function() {
				return (int) ($this->bujur / 15);
			}],
			[['timeZone'], 'integer', 'min' => -12, 'max' => 12],
			[['rawOffset'], 'default', 'value' => function() {
				return $this->timeZone * 3600;
			}]
		];
	}

	public function __construct( $args = array() )
	{
		foreach ($args as $key => $value)
			$this->{$key} = $value;

		// fill default value, using Jakarta

		if ( empty($this->lintang ) )
			$this->lintang = -6.2115;

		if ( empty($this->bujur ) )
			$this->bujur = 106.8452;

		if ( empty($this->timestamp ) )
			$this->timestamp = date('U');

		if ( empty($this->date ) )
			$this->date = date('d/m/Y', $this->timestamp);

		if ( empty($this->timeZone ) )
			$this->timeZone = (int) ($this->bujur / 15);

		if ( empty($this->rawOffset ) )
			$this->rawOffset = $this->timeZone * 3600;
	}

	/**
	 * Sudut deklinasi matahari. Satuan derajat.
	 * @return float
	 */
	public function getDelta()
	{
		$u = ($this->timestamp - ($this->bujur * 240) - 946684800) / self::YEAR_LENGTH;
		$T = 2 * pi() * $u;

		$delta = 0.37877 + 23.264 * SIN($T - 1.38835706) + 0.3812 * SIN(2 * $T - 1.443073132) + 0.17132 * SIN(3 * $T - 1.042345536);
		return $delta;
	}

	/**
	 * Equation time. Satuan detik.
	 * @return float
	 */
	public function getET()
	{
		$u = ($this->timestamp - ($this->bujur * 240) - 946684800) / self::YEAR_LENGTH;

		$l0 = 2 * pi() * (0.779072417 + 1.000021383 * $u);

		$sub1 = -(107.34 + 0.1422 * $u) * SIN($l0) - (428.76 - 0.0372 * $u) * COS($l0);
		$sub2 = (596.04 - 0.0084 * $u) * SIN(2 * $l0) - (1.74 + 0.003 * $u) * COS(2 * $l0);
		$sub3 = (4.44 + 0.006 * $u) * SIN(3 * $l0) + (19.2 - 0.0024 * $u) * COS(3 * $l0);
		$sub4 = - 12.72 * SIN(4 * $l0);

		$et = $sub1 + $sub2 + $sub3 + $sub4;

		return $et;
	}

	/**
	 * Menghitung waktu pada saat matahari pada sudut `$angle` dari titik tertinggi.
	 * @param float $dzuhur
	 * @param float $delta
	 * @param float $angle
	 * @return float Waktu dalam detik
	 */
	public function getTimeOfAngle($dzuhur, $delta, $angle)
	{
		$angle = $angle * pi() / 180;
		$delta = $delta * pi() / 180;
		$lintang = $this->lintang * pi() / 180;
		$cosTeta = (cos($angle) - sin($lintang) * sin($delta)) / (cos($lintang) * cos($delta));
		if ($cosTeta < -1 || $cosTeta > 1) {
			return;
		}
		$teta = acos($cosTeta) * 180 / pi();
		$time = $teta * 240;

		return $angle >= 0 ? $dzuhur + $time : $dzuhur - $time;
	}

	public function getImsakiyah()
	{
		// dzuhur
		$dzuhur = (12 * 3600) + $this->rawOffset - ($this->bujur * 240) - $this->getET();
		$delta = $this->getDelta();
		$result = [];

		// $alfa = sudut matahari dari posisi tertinggi
		// fajar / shubuh, $alfa = -90 - 20
		$alfa = -110;
		$result['shubuh'] = $this->getTimeOfAngle($dzuhur, $delta, $alfa);

		// sudut pembiasan
		$sp = 0.833 + 0.0347 * sqrt($this->ketinggian);

		// terbit matahari, $alfa = -90 - sudut pembiasan
		$alfa = -90 - $sp;
		$result['terbit'] = $this->getTimeOfAngle($dzuhur, $delta, $alfa);

		// dhuzur
		$result['dzuhur'] = $dzuhur;

		// ashar, panjang bayangan = panjang benda + panjang bayangan saat dzuhur.
		$aAlfa = 1 + abs(tan(($delta - $this->lintang) * pi() / 180));
		$alfa = atan($aAlfa) * 180 / pi();
		$result['ashar'] = $this->getTimeOfAngle($dzuhur, $delta, $alfa);

		// maghrib, $alfa = 90 + sudut pembiasan
		$alfa = 90 + $sp;
		$result['maghrib'] = $this->getTimeOfAngle($dzuhur, $delta, $alfa);

		// isya', $alfa = 90 + 18
		$alfa = 108;
		$result['isya'] = $this->getTimeOfAngle($dzuhur, $delta, $alfa);

		return $result;
	}
}