<?php
/**
* Compute the phase of the terran moon for a given epoch.
*
* $moon = new PhutilLunarPhase(time());
* $moon->isFull();
*/
final class PhutilLunarPhase extends Phobject {
private $epoch;
public function __construct($epoch) {
$this->epoch = $epoch;
}
private function getPhase() {
// (Aug 11, 1999) A new moon.
$new_moon_epoch = 934354800;
// Number of seconds in the lunar phase.
$phase_length = 2551442.8768992;
return fmod($this->epoch - $new_moon_epoch, $phase_length) / $phase_length;
}
public function isFull() {
return abs($this->getPhase() - 0.5) < 0.02;
}
public function isNew() {
return $this->getPhase() < 0.02 || $this->getPhase() > 0.98;
}
public function isWaxing() {
return $this->getPhase() < 0.5;
}
public function isWaning() {
return $this->getPhase() > 0.5;
}
}