<?php

class TimeTravel {
	public $start;
	public $end;

  public function __construct($date1, $date2 = "") {
		$this->start = new DateTime($date1);
		$this->end = new DateTime($date2);
  }

	public function getTravelInfo() {
		$interval = $this->start->diff($this->end);
		return "Il y a " . $interval->y . " années, " . $interval->m . " mois, " . $interval->d . " jours, " . $interval->h . " heures, " . $interval->i . " minutes, et " . $interval->s . " secondes entre les deux dates.<br>";
	}

	public function findDate($interval) {
		if($interval>=0){
			$newInterval = DateInterval::createFromDateString($interval);
			$this->end = $this->start->sub($newInterval);
		} else {
			$interval *= -1;
			$newInterval = DateInterval::createFromDateString($interval);
			$this->end = $this->start->add($newInterval);
		}
		return $this->end;
	}

	public function backToFutureStepByStep($step) {
		$today = new DateTime();
		$array = [];
		$array[0] = $this->start;
		$newStep = new DateInterval($step);
		for($i=1; $array[$i-1]<$today; $i++) {
			$temp = clone $array[$i-1];
			$array[$i] = $temp->add($newStep);
		}

		return $array;
	}
};

$travel = new TimeTravel("1985/12/31", "today");
echo $travel->getTravelInfo();

//$datePast = $travel->findDate('1000000000 seconds');
//echo $datePast->format('d/m/Y');
$travel->findDate('1000000000 seconds');
echo $travel->end->format('d/m/Y');

$timeArray = $travel->backToFutureStepByStep('P1M1W1D');
foreach($timeArray as $element) {
	echo "<br>" . $element->format('M d Y A H:i');
}