<?php

class TimeTravel {

    private $start;
    private $end;

    public function __construct(DateTime $startDate, DateTime $endDate) {

        $this->startDate = $startDate;
        $this->endDate = $endDate;
    }


    public function getTravelInfo():string {
        $diff = $this->startDate->diff($this->endDate);
        return $diff->format('Il y a %y années, %m mois, %d jours, %h heures, %i minutes et %s secondes entre les deux dates');
    }

    public function findDate(int $interval):DateTime {

        $dateInterval = new DateInterval('PT' . $interval .'S' );
        return $this->startDate->sub($dateInterval);

    }

    public function backToFutureStepByStep($step):array {

        $result = [];
        $dateRange = new DatePeriod($this->startDate, $step, $this->endDate);

        foreach ($dateRange as $date) {

            $result[] = $date->format('M-d-y A-i:H:s');

        }
        return $result;
    }

}


$timeTrip = new TimeTravel(new DateTime('1985-12-31'), new DateTime());
echo $timeTrip->getTravelInfo();

$retour = $timeTrip->findDate(1000000000);
echo "<br>". $retour->format("Y-m-d") . "<br>";

$convecteur = $timeTrip->backToFutureStepByStep(new DateInterval('P1M1W1D'));
var_dump($convecteur);